In recent years there has been much progress on the investigation of the QCD phase diagram with lattice QCD. This talk will focus on the developments in the last few years. Especially the addition of external influences and extended ranges of $T$ and $\mu$ yield an increasing number of interesting results, a subset of which will be discussed. Many of these conditions are important for the...
New incarnations of heavy-ion collision experiments are turning our attention to hard processes and a more fine-grained resolution of the QGP. In this endeavor quarkonia or open heavy flavors turn out to be versatile probes, which are usually described through models based on perturbative QCD, AdS, and effective field theories. The lattice provides nonperturbative input and constraints to such...
The leading hadronic vacuum polarisation contribution to $(g-2)_\mu$
was recently determined by the Budapest-Marseille-Wuppertal
collaboration to sub-percent precision, providing for the first
time an ab-initio calculation of this quantity with errors comparable
to phenomenological determinations.
To reach this unprecedented level of precision, a number of
critical issues needed to be...
We discuss recent progress in Tensor Lattice Field Theory and economical, symmetry preserving, truncations suitable for quantum computations/simulations. We focus on spin and gauge models with continuous Abelian symmetries such as the Abelian Higgs model and emphasize noise-robust implementations of Gauss's law. We discuss recent progress concerning the comparison between field digitizations...
Excited state contamination is one of the most challenging sources of systematics to tackle in the determination of nucleon matrix elements and form factors.
The signal-to-noise problem prevents one from considering large source-sink time separations.
Instead, state-of-the-art analyses consider multi-state fits.
Excited state contributions to the correlation functions are particularly...
We present results for $\eta$ and $\eta^\prime$ masses at the physical point.
The two independent decay constants, e.g., for the flavour singlet/non-singlet
basis, are also computed for both particles. The chiral and continuum limit extrapolation is performed on 21 CLS $n_f = 2+1$ Wilson Clover improved ensembles at four different lattice spacings and along two quark mass trajectories,...
The broad class of U(N) and SU(N) Polyakov loop models on the lattice
are solved exactly in the combined large N, Nf limit, where N is a number
of colors and Nf is a number of quark flavors, and in any dimension.
In this 't Hooft-Veneziano limit the ratio N/Nf is kept fixed. We calculate
both the free energy and various correlation functions. The critical behavior
of the models is...
In this talk we present in detail the continuum extrapolation procedure of the
recent determination of the leading order hadronic vacuum polarization contribution to the muon anomalous magnetic moment from the Budapest-Marseille-Wuppertal collaboration (arxiv:2002.12347).
We consider a dual representation of an effective three-dimensional Polyakov loop model for the SU(3) theory at nonzero real chemical potential. This representation is free of the sign problem and can be used for numeric Monte-Carlo simulations. These simulations allow us to locate the line of second order phase transitions, that separates the region of first order phase transition from the...
The paradigm of effective field theory is one of the most powerful tools available in physics. While most commonly employed in parametrizing renormalization group flow, it is also of great utility in describing dispersive systems such as $K_0 - \bar{K}_0$ states that both oscillate and decay. Of particular interest for the lattice community is the study of field theories off the real axis of...
Using an SU(3) flavour symmetry breaking expansion between the strange and light quark masses, we determine how this constrains the extrapolation of baryon and meson octet matrix elements and form factors. In particular we can construct certain combinations, which fan out from symmetric point (when all the quark masses are degenerate) to the point when the light and strange quarks take their...
We present results of gluonic and pseudoscalar matrix elements of the $\eta$ and $\eta'$ mesons at the physical quark mass point, in the continuum limit. The simulations are carried out on $n_f=2+1$ CLS ensembles, with non-perturbatively improved Wilson fermions. We discuss the renormalization of these quantities and check the consistency with the singlet and non-singlet axial Ward identities....
In the strong coupling and heavy quark mass regime, lattice QCD reduces to a 3 dimensional theory of Polyakov loops. We apply coarse graining techniques to such theories in 1 and 2 dimensions at finite temperature and non-zero chemical potential.
In 1 dimension the method is applied to the effective theory up to $\mathcal{O}(\kappa^4)$, where $\kappa$ is the hopping parameter of the original...
We present an update, from the Fermilab Lattice, HPQCD, and MILC collaborations, of our results for the light-quark, connected contribution to the hadronic vacuum polarization correction to the muon’s anomalous magnetic moment. The calculation is performed on 2+1+1 highly-improved staggered quark (HISQ) ensembles with physical pion mass at four lattice spacings (0.15fm-0.06fm). We also present...
We report on the recent progress of our analysis into nucleon sigma terms, as well as the singlet axial and tensor nucleon charges. These are extracted from the CLS gauge configurations, which utilise the Lüscher-Weisz gluon action and the Sheikholeslami-Wohlert fermion action with $N_f = 2 + 1$ fermions, with pion masses ranging from the physical value up to 410 MeV, and lattice spacings...
Some aspects of quantum systems with non-unitary dynamics are well-described by non-Hermitian effective Hamiltonians. Such systems contain a wealth of interesting physics such as their phase structure, eg. QCD at finite Baryon density, which describes cores of neutron stars. Classical simulation of general non-Hermitian Hamiltonians is rendered difficult, and in some cases, impossible due to...
We measure the spatial distribution of all components of the color fields surrounding a static quark–antiquark pair in QCD with (2+1) HISQ flavors.
We isolate the nonperturbative component of the longitudinal chromoelectric
color field responsible for the linear term in the confining potential.
We present generalizations of Hamiltonian Lattice QCD as derived from the continuous time limit of strong coupling lattice QCD: we discuss the flavor dependence and the effect of gauge corrections. This formalism is applied at finite temperature and baryon density and allows both for analytic and numeric investigations that are sign problem-free.
Preliminary results are presented for nucleon isovector charges and twist-2 matrix elements which have been obtained employing an improved analysis strategy to deal with excited state contamination. The set of CLS N_f=2+1 gauge ensembles in this study has been extended compared to our 2018 calculation, including an ensemble at physical quark masses. Besides the addition of new ensembles, the...
It has long been known that there is a phase transition between confined and unconfined phases of compact pure gauge QED on the lattice. In this work we report three manifestations of this phase change as seen in the Landau gauge photon propagator, the static potential, and distribution of Dirac Strings in the gauge fixed configurations. Each of these was calculated with large lattices with...
Open lattice field theories are useful in describing many physical systems. Yet their implementation in traditional quantum computing is hindered by the requirement of Hermiticity. One method used to overcome this is embedding the non-Hermitian system within a larger Hermitian system by introducing ancillary qubits. We implement the transverse Ising Model with an addition of an imaginary...
We present updated results for the light-quark connected part of the leading hadronic contribution to the muon g−2 from configurations with 2+1+1 flavors of HISQ quarks using the time-momentum representation of the electromagnetic current correlator. We have added statistics on two ensembles as well as a fourth lattice spacing using configurations that have been generated by the MILC...
We present updates on the calculation of flavor diagonal axial, tensor and scalar nucleon charges $g_{A,S,T}^{u,d,s}$ focusing on understanding the excited state contamination (ESC) including contributions of possible low-lying ($N\pi$ and $N\pi\pi$) excited states to individual nucleon matrix elements.
QCD at fixed baryon number can be formulated in terms of transfer matrices explicitly defined in the canonical sectors. In the heavy-dense limit, the fermionic contributions to the canonical partition functions can be calculated analytically in terms of Polyakov loops. It turns out that at low temperatures and infinitely strong coupling the sign problem is exponentially reduced by many orders...
Recently, the hadronic vacuum polarization contribution to the anomalous
magnetic moment of the muon was determined by the BMW collaboration with
sub-percent precision. Such a precision requires to
control many sources of uncertainty. One of these is the uncertainty
in the determination of the lattice spacing.
In this talk, we present the scale setting entering this computation....
We present a major update on the spectrum of the closed flux-tube in $D=3+1$ $SU(N)$ gauge theories. Namely, we calculate the excitation spectrum of a confining flux-tube which winds around a spatial torus as a function of its length $l$, for short as well as long tubes. We do so for $N=3,5,6$ and two different values of the lattice spacing. Our states are characterised by the quantum numbers...
The possibility for near-term quantum simulations in lattice field theory depends upon efficiently using the limited resources available. In this talk, we will discuss how approximating lattice gauge theories like SU(3) with discrete subgroups can be theoretically analyzed as a lattice effective field theory. Further, methods for implementation upon quantum hardware will be covered. Numerical...
Starting with a summary of our studies of the sensitivity of various charges and form factors to the excited state spectrum, including input from PCAC, vector meson dominance and chiral perturbation theory, I will present an update on results for nucleon charges and form factors.
Pure gauge theories are rather different from theories with pure scalar and fermionic matter, especially in terms of the nature of excitations. For example, in scalar and fermionic theories, one can create ultra-local excitations. For a gauge theory, such excitations need to be closed loops that do not violate gauge invariance. In this talk, we present a study on the condensation phenomenon...
The Schwinger model is a testbed for the study of quantum gauge field theories. We give scalable, explicit digital quantum algorithms to simulate the lattice Schwinger model in both NISQ and fault-tolerant settings. In particular, we analyze low-order Trotter formula simulations of the Schwinger model, using recently derived commutator bounds, and give upper bounds on the resources needed for...
The infamous strong CP problem in particle physics can in principle be solved by a massless up quark. In particular, it was hypothesized that topological effects could substantially contribute to the observed nonzero up-quark mass without reintroducing CP violation. Alternatively to previous work using fits to chiral perturbation theory, in this talk we present direct lattice QCD computations...
Thimble regularisation of Yang Mills theories is still to a very large extent terra incognita. We will discuss a couple of topics related to this big issue. 2d YM theories are in principle good candidates as a working ground. An analytic solution is known, for which one can switch from a solution in terms of a sum over characters to a form which is a sum over critical points. We would be...
Confinement remains one the most interesting and challenging nonperturbative phenomenon in non-Abelian gauge theories. Recent semiclassical (for $SU(2)$) and lattice (for QCD) studies have suggested that confinement arises from interactions of statistical ensembles of instanton-dyons with the Polyakov loop. In this talk, I will present recent work which has extended the study of semiclassical...
The low-lying Dirac modes become localised at the finite-temperature transition in QCD and in other gauge theories, suggesting a general connection between their localisation and deconfinement. The simplest model where this connection can be tested is $\mathbb{Z}_2$ gauge theory in 2+1 dimensions. We show that in this model the low modes in the staggered Dirac spectrum are delocalised in the...
Proton decay is a long-sought manifestation of baryon number violation predicted by Grand Unification and expected due to baryon asymmetry of the Universe. Amplitudes of such decay in various channels depend on proton structure determined by nonperturbative QCD dynamics and have to be determined on a lattice. We report results of a recent calculation of these amplitudes using chirally...
Computing conformal dimensions $D(j_L,j_R)$ of local fields that transform in an irreducible representation of $SU(2) \times SU(2)$ labeled with $(j_L,j_R)$ at the $O(4)$ Wilson-Fisher fixed point has become interesting recently, especially when $j_L$, $j_R$ become large. These calculations are challenging in the traditional lattice $O(4)$ model. We can overcome these difficulties by using a...
In recent years, lattice determinations of non-perturbative quantities such as $f_K$ and $f_\pi$, which are relevant for $V_{us}$ and $V_{ud}$, have reached an impressive precision of O(1%) or better. To make further progress, electromagnetic and strong isospin breaking effects must be included in lattice QCD simulations.
We present the status of the RBC&UKQCD lattice calculation of...
We show that in the vicinity of the deconfinement transition the behaviour of the interquark potential in pure lattice gauge theories can be precisely predicted combining results from Conformal Field Theory, Effective String Theory and Integrable Models. We compare these predictions with simulations of the SU(2) gauge model both in (2+1) and in (3+1) dimensions.
We provide strong evidence that the asymptotically free (1+1)-dimensional non-linear O(3) sigma model can be regularized using a quantum lattice Hamiltonian, referred to as the "Heisenberg-comb", that acts on a Hilbert space with only two qubits per spatial lattice site. The Heisenberg-comb consists of a spin-half anti-ferromagnetic Heisenberg-chain coupled anti-ferromagnetically to a second...
We have implemented and are computing nucleon 3pt functions using the stochastic Laplacian Heaviside (sLapH) method. Such a technique enables the use of momentum space creation and annihilation operators providing access to the Breit-Frame as well as full control of the spin of the initial and final operator. It also enables the use of multi-hadron operators, for example the problematic N-pi...
We present a lattice QCD calculation of the axial $\gamma$W-box diagrams relevant for the kaon semilep-leptonic decays. We utilize a recently proposed method, which connects the electroweak radiative corrections in Sirlin's representation to that in chiral perturbation theory. It allows us to use the axial $\gamma$W-box correction in the SU(3) limit to obtain the low energy constants for...
Determining the existence and the location of the QCD critical point remains a major open problem, both theoretically and experimentally. In this talk, I present a new way of reconstructing the equation of state in the vicinity of the nearest singularity (the Lee-Yang edge singularity in the crossover region) from a truncated Taylor series expansion for small $\mu$. This is done by using a...
Hamiltonian formulation of lattice gauge theories provides the natural framework for the purpose of quantum simulation, an area of research that is growing with advances in quantum-computing algorithms and hardware. It is therefore important to identify the most accurate, while computationally economic, Hamiltonian formulation(s) of lattice gauge theories along with necessary truncation...
The gauge-invariant formulations of lattice field theories provide a way to study real-time dynamics using a smaller effective Hilbert space. This allows for more information to be encoded for the same quantum resources as a non-gauge invariant forumlation which will be important for simulations on Noisy Intermediate Scale Quantum (NISQ) computers. While qubit-based hardware is currently the...
We calculate the $B\to D^{(*)}\ell\nu$ form factors in 2+1 flavor
relativistic lattice QCD by employing the Moebius domain-wall action
for all quark flavors. Our simulations are carried out at lattice cut-offs
$a^{-1} \sim 2.5$, 3.6 and 4.5 GeV with varying bottom quark masses
up to 0.7 $a^{-1}$ to study heavy quark mass dependence and
discretization effects. We extrapolate the form...
Quantum technologies offer the prospect to efficiently simulate sign-problem afflicted phenomena, such as topological terms, chemical potentials, and out-of-equilibrium dynamics. In this work, we derive the 3+1D topological $\theta$-term for Abelian and non-Abelian lattice gauge theories in the Hamiltonian formulation, paving the way towards Hamiltonian-based simulations of such terms on...
We highlight QCDSF/UKQCD Collaboration's recent developments on computing the Compton amplitude directly via an implementation of the second-order Feynman-Hellmann theorem. As an application, we compute the nucleon Compton tensor across a range of photon momenta at an unphysical quark mass. This enables us to study the $Q^2$ dependence of the low moments of the nucleon structure functions in a...
Quantum link models (QLMs) are extensions of Wilson-type lattice gauge theories, and show rich physics beyond the phenomena of conventional Wilson gauge theories. Here we explore the physics of U(1) symmetric QLMs, both using a more conventional quantum spin-1/2 representation, as well as a fermionic representation. In 2D, we show that both bosonic and fermionic QLMs have the same physics. We...
In the Hamiltonian formulation, free spin-1/2 massless Dirac fermions on a bipartite lattice have an $O(4)$ (spin-charge) symmetry. Lattice interaction terms usually break this symmetry down to some subgroups. For example, the Hubbard interaction at half-filling breaks the symmetry down to $SO(4)$ by breaking the spin-charge flip symmetry. In this work, we construct a lattice model with a new...
We present preliminary results for the kaon semileptonic form factors
using one of the PACS10 configuration sets, whose physical volume is
(10.2 fm)$^4$ at the physical point with the lattice spacing of 0.064 fm.
The configuration was generated using the Iwasaki gauge action and $N_f=2+1$
stout-smeared clover quark action. The value of |$V_{us}$| is determined
using the interpolated...
In order to simulate quantum field theories using quantum computers, a regularization of the target space of the field theory must be obtained which admits a representation in terms of qubits. For the 1+1 dimensional nonlinear sigma model, there have been several proposals for how such a regularization may be achieved. The fuzzy sphere regularization proposes to represent the Hilbert space of...
Lattice QCD calculations of the nucleon electromagnetic form factors are of interest at the high and low momentum transfer regions. For high momentum transfers especially there are open questions, such as the zero crossing in the proton's electric form factor, which require more calculations. We will present recent progress from the QCDSF/UKQCD/CSSM collaboration on the calculations of these...
Two important sources of systematic errors in lattice QCD calculations of radiative leptonic decays are unwanted exponentials in the sum over intermediate states and unwanted excited states created by the meson interpolating field. Performing the calculation using a 3d sequential propagator allows for better control over the systematic uncertainties from intermediate states, while using a 4d...
In the Hamiltonian picture, free spin-1/2 Dirac fermions on a bipartite lattice have an O(4) (spin-charge) symmetry. Here we construct an interacting lattice model with an interaction V, which is similar to the Hubbard interaction but preserves the spin-charge flip symmetry. By tuning the coupling V, we show that we can study the phase transition between the massless fermion phase at small V...
We report on the use of Feynman-Hellmann techniques to calculate the off-forward Compton amplitude (OFCA) in lattice QCD. At leading-twist, the Euclidean OFCA is parameterised by moments of generalised parton distributions (GPDs). Hence this calculation provides the opportunity to determine GPD-related quantities from first principles.
Quantum simulation has the promise of enabling access to Minkowski-time dynamical observables in quantum field theories. Progress in devising and benchmarking quantum-simulation proposals, in form of analog protocols or digital algorithms, is ongoing, and increasingly complex theories are being targeted towards the goal of simulating QCD. In this talk, I will introduce a hybrid analog-digital...
We calculate $K \to \pi\pi$ matrix elements using periodic boundary conditions as an independent calculation from our previous calculation with G-parity boundary conditions. We present our preliminary results for physical masses on a $24^3, a^{-1}=1$ GeV, $2+1$-flavor Mobius DWF ensemble generated by the RBC and UKQCD collaborations and discuss the prospect for high-precision computation of...
We report our study on critical endpoints of finite temperature phase transitions in (2+1)- and 4-flavor QCD with Wilson-Clover fermions. As an extension of our previous calculations on coarser lattices, we performed our simulations on lattices with temporal extents of 8 and 10 for 2+1 and 4 flavors, respectively, to carry out continuum extrapolations more precisely. For the calculation in...
I present lattice Monte Carlo evidence of localized quantum excitations of the fields surrounding static electric charges in the q=2 abelian Higgs model; such excitations would appear as excited states of isolated fermions. Since the q=2 abelian Higgs model is a relativistic version of the Landau-Ginzburg effective model of superconductivity, these results may have some application in a...
When non-Abelian gauge fields in $SU(3)$ QCD have a line-singularity leading to non-commutability with respect to successive partial-derivative operations, the non-Abelian Bianchi identity is violated. The violation as an operator is shown to be equivalent to violation of the Abelian-like Bianchi identities. Then there appear eight Abelian-like conserved magnetic monopoles of the Dirac type in...
We introduce a new method to calculate phase shifts on noisy intermediate scale quantum (NISQ) hardware platforms using a wave packet edge time delay. The method uses the early and intermediate stages of the collision because the standard method based on the asymptotic out-state behavior is unreachable using today’s NISQ platforms. The calculation was implemented on a 4-site transverse Ising...
Understanding of the QCD phase diagram is one of important topics in nuclear and hadron physics.
In particular, various possible phase structures are proposed from analyses of effective theories in low temperature and high density region. One of them is inhomogeneous chiral condensate which exhibits characteristic space structures. Since there is no general established method for...
Lattice gauge scalar models allow analytical connection between confinement region and Higgs region for gauge invariant operators.
Combining the cluster expansion and the duality, we try to understand non-trivial contribution from scalar field in quark confinement mechanism.
In order to understand quark confinement further, moreover, we study double-winding Wilson loop averages in the...
To investigate the properties of the large $N$ limit of $\mathcal{N}=1$ SUSY Yang-Mills theory, we have started a feasibility study for a reduced matrix model with an adjoint Majorana fermion. The gauge action is based on the Wilson action and the adjoint-fermion is the Wilson-Dirac action on a reduced lattice with twisted gauge boundary condition. We employ the RHMC algorithm in which the...
Dimensionally reducing gauge theories like QED or Yang-Mills theory on small spatial tori often yields simple quantum mechanical models that retain some of the interesting structure of the parent gauge theory. 2D electrodynamics with massive charge-N matter, for example, leads to the quantum mechanics of a particle on a circle with a Z_N potential and a theta-term. This model, despite being...
Observation of neutrinoless double-beta $(0\nu\beta\beta)$ decay, a beyond the standard model process that violates lepton number conservation, would imply that neutrinos are Majorana fermions. In order to draw reliable conclusions from the current experimental limits and potential future discoveries, it is important to reduce the uncertainties in the theoretical predictions of its decay rate....
The Lorentzian type IIB matrix model is a promising candidate for a non-perturbative formulation of superstring theory. In previous studies, Monte Carlo calculations provided interesting results indicating the spontaneous breaking of SO(9) to SO(3) and the emergence of (3+1)-dimensional space-time. However, an approximation was used to avoid the sign problem, which seemed to make the...
Future quantum computers may serve as a tool to access non-perturbative real-time correlation functions. In this talk, we discuss the prospects of using these to study Compton scattering for arbitrary kinematics. In particular, the need to restrict the size of the spacetime in quantum computers prohibits a naive determination of such amplitudes. However, we present a practical solution to this...
We present results for the neutron electric dipole moment due to the to dimension 4 and dimension 6 gluonic CP violation, and the isovector quark chromoelectric dipole moment using clover valence quarks on HISQ dynamical ensembles. For the gluonic operators, we use the gradient flow scheme to obtain divergence-free continuum results. For the chromoelectric dipole moment operator, we use the...
We propose a subvolume method to study the $\theta$ dependence of the free
energy density of the four-dimensional SU($N$) Yang-Mills theory on the lattice.
As an attempt, the method is first applied to SU(2) Yang-Mills theory at
$T=1.2\,T_c$ to understand the systematics of the method. We then proceed to
the calculation of the vacuum energy density and obtain the $\theta$...
We will present preliminary findings on improving the lattice calculation of the neutron electric dipole moment from the θ term in QCD. The neutron EDM is highly correlated with the lowest lying modes of the Dirac operator. We take advantage of this with a full volume sampling for the low mode part of the quark propagator in order to increase statistics. This augments the all-mode averaging...
We present a complete and scalable quantum algorithm for the simulation of SU(2) gauge bosons coupled to fermionic matter in one spatial dimension. To represent the gauge fields, we find it is more practical to start from their Schwinger boson formulation, rather than the more conventional Kogut-Susskind rigid rotor formulation. Within this framework, and taking Trotter-Suzuki decomposition...
The type IIB matrix model was proposed as a nonperturbative formulation of superstring theory in 1996. We simulate this model by applying the complex Langevin method to overcome the sign problem. Here, we clarify the relationship between the Euclidean and Lorentzian versions of the type IIB matrix model in a new phase we discovered recently.
Lattice techniques are the most reliable ones to investigate its phase diagram in the temperature-baryon density (chemical potential) plane. They are, however, well-known to be saddled with a variety of problems at nonzero density. I address here the old question of placing the baryonic (quark) chemical potential on the lattice and point out that important consequences for the current and...
The Fermilab experiment recently published their new measurement of the anomalous magnetic moment of the muon, confirming the Brookhaven's measurement with a comparable precision. Combining those two results and using the theory estimate published by the "Muon $g-2$ theory initiative", a discrepancy of about 4 sigmas is observed between experiment and the theory prediction based on the...
We present a lattice QCD calculation of the energy eigenvalues of the dibaryon system using the gauge ensembles generated with the domain wall fermion action. Using the sparsening field method, multiple dibaryon interpolating operators are used to reduce the contamination from excited states. Some relevant results for the weak transition matrix elements of the dibaryon system are also shown.
Gauge theories admit a generalisation in which the gauge group is replaced by a finer algebraic structure, known as a 2-group. The first model of this type is a Topological Quantum Field Theory introduced by Yetter. I would like to discuss a common generalisation of both the Yetter’s model and Yang-Mills theory. I will focus on the lattice formulation of such model for finite 2-groups. After...
In this work we study the large $N_c$ scaling of pion-pion scattering lengths for $N_f=4$ degenerate quark flavours. We focus on the standard isospin-2 channel and the adjoint-antisymmmetric representation, which is unique for $N_f \geq 4$. We compare the results obtained for two regularisations (Wilson and Twisted-Mass) and three values of the lattice spacing, and observe significant...
The Euclidean time windows defined in RBC/UKQCD 2018 provide a means to test the consistency of different lattice results as well as the consistency with the data-driven R-ratio results on a short timescale. This is of particular urgency due to an apparent emerging tension between data-driven results and some lattice results. I will present an update to the 2018 RBC/UKQCD result for Euclidean...
Nucleon isovector form factors calculated on 2+1-flavor domain-wall fermion (DWF) numerical lattice-QCD ensemble with phyaical up-, down- and strange-quark mass and lattice momentum cut off of about 1.730(4) GeV will be reported.
In this talk, I discuss a simple model based on the symmetry group $Z_2$ belonging to the class of 2-group gauge systems. Particular limits of such systems correspond to certain types of topological quantum field theories. In the selected model, independent degrees of freedom are associated to both links and faces of a four-dimensional lattice and are subject to a certain constraint. I present...
We present an update on our efforts to determine the QCD phase diagram using complex Langevin simulations. In this study, we use two flavours of Wilson fermions with moderate pion masses ($\sim 450$ MeV). To improve the convergence of the simulations, we employ adaptive step size scaling and dynamic stabilisation. Here we report on our findings at higher temperatures and density. In addition,...
Finite-volume scattering at physical pion mass is still an exploratory field in lattice QCD. This generally involves the extraction of excited states through multi-particle correlators on systems with resonances. In that context, distillation has demonstrated to be effective both as a smearing kernel and a computational tool. Motivated by the study of the smearing profile of the distillation...
The Thirring model describes relativistic fermions with a contact interaction between conserved fermion currents. In 2+1 spacetime dimensions its U($2N$) global symmetry is broken at strong coupling to U($N)\otimes$U($N$) through generation of a non-vanishing bilinear condensate $\langle\bar\psi\psi\rangle\not=0$. I present results of numerical simulations of the single-flavour model using...
All methods currently used to study finite baryon density lattice QCD suffer from uncontrolled systematic uncertainties in addition to the well-known sign problem. We formulate and test a method - sign reweighting - that works directly at finite chemical potential and is yet free from any such uncontrolled systematics: with this approach the only problem is the sign problem itself. In practice...
We present a lattice calculation of the Euclidean position-space windows contributing to the leading-order hadronic vacuum polarization term of the muon anomalous magnetic moment $a_\mu$.
Short-, intermediate- and long-distance windows are considered in order to isolate different scales sensitive to specific integration ranges of experimental time-like data used in the R-ratio.
By adopting...
The scattering length is an important quantity that describes scattering at low energies. We will present our evaluation of the $K\pi$ scattering length in the isospin $I=\frac12$ and $I=\frac32$ channels. The computation uses the RBC-UKQCD 2+1-flavour ensembles with Domain Wall Fermions at near-physical quark masses. With the help of all-to-all methods, we construct the correlation functions,...
Modelling the behaviour of strongly interacting fermion sytems with correct symmetry properties presents significant challenges for lattice field theories. Investigating the suitability of domain wall fermions, we explore the locality and the Ginsparg-Wilson error of the Dirac operator in the context of a dynamical 2+1D non-compact Thirring model. We further investigate the eigenvalues of the...
In the analysis of (lattice) QCD observables very often chiral perturbation theory (ChPT) is heavily used to describe the quark mass dependence or relate different observables via symmetry relations. Within ChPT the low energy constants (LECs) play a crucial role and their precise knowledge is important in lattice QCD as well as in phenomenology. While there are many lattice determinations of...
The first results from the Fermilab E989 experiment have confirmed the long-standing tension between the experimental determination of the muon anomalous magnetic moment $a_\mu=(g_\mu-2)/2$ and its SM determination using the dispersive approach. In order to match the expected final precision from E989, the current uncertainty on ab initio determinations using lattice QCD must be decreased by a...
In typical statistical mechanical systems the grand canonical partition function at finite volume is proportional to a polynomial of the fugacity $\exp(μ/T)$. The zero of this Lee-Yang polynomial closest to the origin determines the radius of convergence of the Taylor expansion of the pressure around $μ=0$. Rooted staggered fermions, with the usual definition of the rooted determinant, do not...
The phase diagram and the location of the critical endpoint of lattice QCD was determined earlier with unimproved staggered fermions on a Nt=4 lattice with the multiparameter reweighting method by studying Fisher zeros. In our recent work, as an extension of the old analysis we introduced stout smearing in the fermion action in order to reduce the finite lattice spacing effects. In this talk...
The study of the Compton amplitude has gained attention in recent years. It plays a central role in the analysis of many fundamental problems such as, for example, the evaluation of the Lamb shift in muonic hydrogen, or the calculation of the proton-neutron mass difference. Hence, the calculation of this amplitude on the lattice would definitely contribute to the solution of the above...
We present a finite volume spectroscopy calculation of I=1 pi-pi scattering utilizing the (stochastic) distillation framework on close to physical and physical point N_f = $2+1$ CLS ensembles. Using the finite volume energy levels, we discuss the long-distance behavior of the vector correlator, which is dominated by the two-pion channel. This part can be accurately constrained using the...
The anomalous magnetic moment of the muon $a_{\mu}$ and the running of the electromagnetic coupling $\alpha$ play a fundamental role in beyond Standard Model (SM) physics searches. Non-perturbative hadronic contributions to both quantities, which are related to the hadronic vacuum polarization (HVP) function consisting of two electromagnetic currents, are a main source of uncertainty in the SM...
The Hubbard model is an important tool to understand the electrical properties of various materials. More specifically, on the honeycomb lattice it features a quantum phase transition from a semimetal to a Mott insulating state which falls into the Gross-Neveu universality class. In this talk I am going to explain how we confirmed said quantum phase transition by taking advantage of recent...
We compute the quark-connected component of the hadronic vacuum polarization function at the energy scale of the Z boson mass in the Schwinger model. This is done by computing different representations of the Adler function on different energy scales. The mass parameters for the different scales are set with a step scaling scheme in which the lattice spacing and volume are adjusted to the...
Recently, the Budapest-Marseille-Wuppertal collaboration has achieved a sub-percent precision in the evaluation of the HVP contribution to the muon g-2. At this level of precision, pure isospin-symmetric QCD is not sufficient. In the talk we will review how QED and strong isospin breaking effects have been included in our work. Isospin-breaking is implemented by expanding the relevant...
We numerically investigate different techniques to extract scattering amplitudes from a Euclidean Lattice $\phi^4$ theory with two fields having different masses. We present an exploratory study of a recently proposed method by Bruno and Hansen for extracting the scattering length from a four-point function (cf. arXiv:2012.11488) and a study of the two and three particle quantization condition.
Deforming the domain of integration after complexification of the field variables is an intriguing idea to tackle the sign problem. In thimble regularization the domain of integration is deformed into an union of manifolds called Lefschetz thimbles. On each thimble the imaginary part of the action stays constant and the sign problem disappears. A long standing issue of this approach is how to...
Quantizing topological excitations beyond a semiclassical approximation is a nontrivial issue. Examples of relevant topological excitations are vortices in (2+1) dimensions. They are the condensed matter analogs of monopoles in particle physics and arise in Bose-Einstein condensates and superfluids. These systems can be described by the (2+1)-d O(2) model, where vortices are present through...
We present a lattice QCD study of $\pi-N$ scattering in the iso-spin $I=3/2$ channel.
The calculation is performed using $N_f=2+1+1$ flavors of twisted mass fermions including an ensemble with
physical pion mass. We compute energy levels for all the moving frames with total momentum up to $\vec{P}=2\pi L(1,1,1)$,
and for all the relevant irreducible representation of the lattice symmetry...
A new approach is presented to explore the singularity structure of lattice QCD at imaginary chemical potential. Our method can be seen as a combination of the Taylor expansion and analytic continuation approaches. Its novelty lies in using rational (Padé) approximants for studying the analytic continuation. The motivation for using rational approximants will be exhibited. We will also try to...
Transition form factors of light pseudoscalar mesons ($\pi^0$, $\eta$ and $\eta^{\prime}$) play a crucial role in computing the hadronic light-by-light contribution to the muon anomalous magnetic moment.
We present first results toward the extraction of these form factors using lattice QCD with staggered fermions on $N_f=2+1+1$ gauge ensembles of the Budapest-Marseille-Wuppertal...
$\mathcal{N}=1$ SUSY Yang-Mills theory is an appealing theoretical framework that has been studied in the literature using different methods, including standard lattice simulations. Among these, the volume-reduced twisted Eguchi-Kawai model, endowed with one adjoint Majorana fermion, could play an important role in studying its large-$N$ limit via the Curci-Veneziano prescription. In this...
In this talk we present a relativistic and model-independent method to analytically derive electromagnetic finite-size effects beyond the point-like approximation. Structure-dependence appears in terms of physical form-factors and derivatives thereof. The values of these physical quantities can be taken either from experimental measurements or auxiliary lattice calculations. We apply our...
Lee-Yang edge singularities have been studied in various spin models to
investigate the analytic structure of the ferromagnetic transition. As
part of the Bielefeld Parma collaboration we investigate Lee-Yang
singularities in lattice QCD. Based on an analytic continuation of the
net-baryon number density, we present results of the location of the
closest singularities in the complex...
The nucleon-pion-state contribution to QCD two-point and three-point functions relevant for lattice calculations of the nucleon electromagnetic form factors are studied in chiral perturbation theory.
To leading order the results depend on a few experimentally known low-energy constants only, and the nucleon-pion-state contribution to the form factors can be estimated. The nucleon-pion-state...
We report on our computation of the pion transition form factor $\mathcal{F}_{\pi \rightarrow \gamma^* \gamma^*}$ from twisted mass lattice QCD, to determine the numerically dominant light pseudoscalar pole contribution for the analysis of hadronic light-by-light scattering in the muon $g-2$. The pion transition form factor is computed directly at the physical point. We present first results...
We report on an ongoing study of the running coupling of SU(N) pure Yang-Mills theory in the twisted gradient flow scheme (TGF). The study exploits the idea that twisted boundary conditions reduce finite volume effects, leading to an effective size in the twisted plane that combines the number of colours and the torus period. We test this hypothesis by computing the TGF running coupling and...
We describe new theoretical opportunities arising from the possibility to solve the gradient flow (GF) equations taking into account the fermion determinant exactly employing non-iterative solvers. Using this exact GF we can find real saddle points of the lattice action at zero chemical potential and trace their evolution in complex space at non-zero chemical potential. We show that these...
The tension between theory and experiment for the anomalous magnetic moment of the muon ($a_\mu$) is one of the long-standing puzzles of modern particle physics. After the update by the Fermilab E989 experiment in April 2021, the discrepancy between both sides lies at the 4.2-sigma level, as of the consensus made in the 2020 muon g-2 theory White Paper. The theory error is entirely dominated...
We present results for the isoscalar electromagnetic form factors of the nucleon computed on the CLS ensembles with $N_\mathrm{f} = 2 + 1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved conserved vector current. In order to estimate the excited-state contamination, we investigate several source-sink separations and apply the summation method. For the...
Taylor expansion of the equation of state of QCD suffers from shortcomings at chemical potentials $\mu_B>(2−2.5) T$. First, one faces difficulties inherent in performing such an expansion with a limited number of coefficients; second,higher order coefficients determined from lattice calculations suffer from a poor signal-to-noise ratio.
We present a novel scheme for extrapolating the equation...
We propose a method to help control cutoff effects in the short-distance contribution to integrated correlation functions, such as the hadronic vacuum polarization, using the corresponding screening correlators computed at finite temperature. The strategy is investigated with Wilson fermions at leading order, which reveals a logarithmically-enhanced lattice artifact in the short-distance...
We investigate the two-flavour Schwinger model in the canonical formulation with fixed fermion number. We use Wilson fermions on the lattice and present a formalism which describes the Dirac operator with dimensionally reduced canonical operators. These reduced operators allow the direct examination of arbitrary meson sectors and the determination of the energy spectrum in each of the sectors....
Taylor expansion in powers of baryon chemical potential ($\mu_B$) is an oft-used method in lattice QCD to compute QCD thermodynamics for $\mu_B\ne0$. We introduce a new way of resumming the contribution of the first $N$ Taylor coefficients to the lattice QCD equation of state to all orders in $\mu_B$. The method reproduces the truncated Taylor expansion when re-expanded in powers of $\mu_B$....
We describe the systematic treatment of the gradient flow at higher orders in perturbation theory and its application within the small flow-time expansion. The results include the coefficients of the gradient-flow definition of the energy-momentum tensor, the quark and the gluon condensates, as well as the hadronic vacuum polarization at next-to-next-to-leading order in the strong coupling....
The hadron resonance gas (HRG) model is often believed to correctly describe the confined phase of QCD. This assumption is the basis of many phenomenological works on QCD thermodynamics and of the analysis of hadron yields in relativistic heavy ion collisions. We use first-principle lattice simulations to calculate corrections to the ideal HRG. Namely, we determine the sub-leading fugacity...
The Hadron Spectrum Collaboration (HSC) presented new results on
two of their ensembles for s-wave scattering phase shifts
in the open-charm sector of QCD. For such ensembles we have made
predictions that are based on the chiral Lagrangian that were published two years ago. In this talk
we confront our phase shifts with those of HSC. A remarkably
consistent picture emerges. In...
As present and future experiments in both the energy and precision frontiers look to identify new physics beyond the Standard Model, they require increasingly precise determinations of fundamental quantities like the electroweak couplings at various momenta. The latter can be obtained from experimental measurements or a particular reference value and the dependence on the energy. A precise,...
We present the nucleon axial and electromagnetic form factors using $N_\textrm{f}=2+1+1$ twisted mass lattice QCD with clover improvement and with quarks with masses tuned to their physical values. Excited state effects are studied using several sink-source separations in the range 0.8 fm - 1.6 fm, exponentially increasing statistics with the separation such that statistical errors remain...
The 1-loop RG flows in the most general local, renormalizable, Euclidean, classically scale invariant and globally SU(N) invariant theory of vector fields is computed. The total number of dimensionless couplings is 7 and several asymptotically free RG flows are found which are not gauge theories but nonetheless perfectly well-defined Euclidean QFT's. The set of couplings is extended to 9 with...
We present a novel method which enables a continuous temperature sampling in a single Monte-Carlo simulation.
The method can be generally used to compute continuous temperature dependence of any observable and we use it to evaluate the temperature dependence of QCD topological susceptibility at very high temperatures.
The various advantages and disadvantages of the method will be...
We investigate the impact of the latest Mainz/CLS collaboration's result for the hadronic vacuum polarization (HVP) on the electroweak (EW) precision tests. The subject is closely related to the muon g-2 via the HVP. Both precision tests come under scrutiny with respect to physics Beyond the Standard Model. Our HVP calculation is used for the running electromagnetic coupling at low energy and...
We present the analysis of isovector axial vector nucleon form factors for a set of $N_f=2+1$ CLS ensembles with $\mathcal O(a)$-improved Wilson fermions and Lüscher-Weisz gauge action. The set of ensembles covers a pion mass range of $M_\pi=130-353\,$MeV with lattice spacings between $a=0.05-0.09\,$fm. In particular, the ensemble list includes a $96^{3}$ box ensemble at the physical pion...
The one-loop determination of the coefficient $c_{\text{SW}}$ of the Wilson quark
action has been useful, in conjunction with non-perturbative
determinations of $c_{\text{SW}}$, to push the leading cut-off effects for on-shell
quantities to $\mathcal{O}(\alpha^2 a)$, or eventually $\mathcal{O}(a^2)$, if no link-smearing is
employed. These days it is common practice to include some...
I will discuss the RBC & UKQCD collaboration's recent lattice calculation of $\epsilon'$, the measure of direct CP-violation in kaon decays. This result significantly improves on our previous 2015 calculation, with nearly 4x the statistics and more reliable systematic error estimates. I will also discuss how our results demonstrate the Standard Model origin of the $\Delta I=1/2$ rule, and will...
The Cabibbo–Kobayashi–Maskawa (CKM) matrix element $|V_{ub}|$ describes the coupling between $u$ and $b$ quarks in the weak interaction, and is one of the fundamental parameters of the Standard Model. $|V_{ub}|$ is the focus of a longstanding puzzle, as the world-average values derived from inclusive and exclusive $B$-meson decays show a tension of a few standard deviations.
Semileptonic...
Exotic states have been predicted before and after the advent of QCD.
In the last decades they have been observed at accelerator experiments in the sector with two heavy quarks, at or above the quarkonium strong decay threshold and called X Y Z states.
These states offer a unique possibility for investigating the dynamical properties of strongly correlated systems in QCD.
I will show how...
This talk will offer an overview of the role of lattice field theory in strongly interacting BSM phenomenology.
I discuss progress in simulating field theories on discrete hyperbolic spaces, with the goal of studying their physics in the bulk, and on the boundary. At tree-level, a free scalar field propagating in the bulk lattice is found to possess power-law two-point correlation functions on the boundary. The power-law behavior excellently matches the expected Klebanov-Witten formula despite being...
Physics colloquium-level lecture on QCD, webcast publicly
Title: QCD: The Glory and The Power
Abstract: After a brief oration in praise of the ideal mathematical beauty of QCD and its imposing experimental success, I will describe several of its ongoing and future applications at the frontiers of knowledge. These are the frontier of precision (muon $g-2$), the frontier of high...
In this talk I examine the algorithmic problem of minimal coupling gauge fields of the Yang--Mills type to Quantum Gravity in the approach known as Causal Dynamical Triangulations (CDT) as a step towards studying, ultimately, systems of gravity coupled with bosonic and fermionic matter. I first describe the algorithm for general dimensions and gauge groups and then focus on the results...
Two-color QCD (QC$_2$D) with two flavors of staggered fermions is studied at imaginary and real quark chemical potential $\mu_q$ and $T>T_c$. Various methods of analytic continuation of the quark number density from imaginary to real quark chemical potentials $\mu_q$ are considered on the basis of the numerical results for imaginary $\mu_q$. At $T < T_{RW} $ we find that the cluster expansion...
We present continuum limit results of the quark mass dependence of octet and decuplet baryon masses obtained from Lattice QCD simulations. This is part of our large-scale programme connected to CLS of simulating $N_f=2+1$ flavours of non-perturbatively improved Wilson fermions where ensembles with large volumes together with a wide range of quark masses, including the physical point, are used....
We develop a gauge covariant neural network for four dimensional non-abelian gauge theory, which realizes a map between rank-2 tensor valued vector fields. We also find the conventional smearing procedures for gauge fields can be regarded as this neural network with fixed parameters. We developed a formula to train the network as an extension of the delta rule, which is used in machine...
We studied the decay rate of the particle decay $B^0 \rightarrow D^- \ell^+ \nu_{\ell}$ using data collected from the Belle Collaboration. In order to analyze this decay rate, we used three parameterizations of the form factor which describes this process, the CLN (Caprini, Lellouch, and Neubert) parametrization, the BGL (Boyd, Grinstein, and Lebed) parametrization, and the BCL (Bourrely,...
Highly oscillatory path integrals are common in lattice field theory. They crop up as sign problems and as signal to noise problems and prevent Monte Carlo calculations of both lattice QCD at finite chemical potential and real-time dynamics. A general method for treating highly oscillatory path integrals has emerged in which the domain of integration of the path integral is deformed into a...
Quantizing gravity is one big problem of theoretical physics and it's well-known that general relativity is not renormalizable perturbatively. Yet studies of quantum gravity on lattice have given evidence of the asymptotic safety scenario in which there is a strongly coupled UV fixed point. In this talk, I will talk about our study of the interaction of two scalar particles propagating on...
In this talk, I will report our group's progress on calculating the nucleon axial form factor with the HISQ action for both valence and sea quarks. Nucleon matrix elements with staggered fermions require careful analysis of the staggered symmetry group. I will report a solution based on the generalized Wigner-Eckart theorem that enables us to extract physical observables from staggered...
In this talk I will discuss several new results from the NPLQCD Collaboration that combine lattice QCD results on (hyper)nuclear systems at unphysical pion masses together with nuclear effective field theories. Two-baryon channels with strangeness $0$ to $-4$ are analized, with findings that point to interesting symmetries observed in hypernuclear forces as predicted in the limit of QCD with a...
The Deep Underground Neutrino Experiment (DUNE) is an upcoming neutrino oscillation experiment that is poised to answer key questions about the nature of the neutrino. Lattice QCD has the ability to make significant impact upon DUNE by computing the interaction of a nucleon to a weak current. Nucleon amplitudes involving the axial form factor are part of the primary signal measurement process...
Complex contour deformations of the path integral have previously been shown to mitigate extensive sign problems associated with non-zero chemical potential and real-time evolution in lattice field theories. This talk details recent extensions of this method to observables affected by signal-to-noise problems in theories with real actions. Contour deformations are shown to result in...
After a brief introduction of Euclidean dynamical triangulations (EDT) as a lattice approach to quantum gravity, I will discuss the emergence of de Sitter space in EDT. Working within the semi-classical approximation, it is possible to relate the lattice parameters entering the simulations to the partition function of Euclidean quantum gravity. This allows to verify that the EDT geometries...
Quenched QCD at zero baryonic chemical potential undergoes a
deconfinement phase transition at a critical temperature $T_c$, which is
related to the spontaneous breaking of the global center symmetry.
Including heavy but dynamical quarks breaks the center symmetry
explicitly and weakens the first order phase transition. For
decreasing quark masses the first order phase transition...
In this work, we obtained the finite temperature Bottomonium interaction potential from the first principle lattice-NRQCD calculation of Bottomonium mass and width [Phys.Lett.B 800, 135119 (2020)]. We find that the HTL complex potential is disfavored by the lattice result, which motives us to employ a model-independent parameterization --- the Deep Neural Network (DNN) --- to represent the...
We present the current status of our ongoing efforts in search of the H-dibaryon on $N_f=2+1$ CLS ensembles away from the SU(3) flavor symmetric point. Utilizing the distillation framework (also known as LapH) in its exact and stochastic forms, we calculate two-point correlation matrices using large bases of bi-local two-baryon interpolators to reliably determine the low energy spectra. We...
We report on an onging study on the interplay between Roberge-Weiss(RW) and chiral transition in simulations of (2+1)-flavor QCD with an imaginary chemical potential. We established that the RW endpoint belongs to the Z(2) universality class when calculations are done with the Highly Improved Staggered Quark (HISQ) action in the Roberge-Weiss plane with physical quark masses. We also have...
The tension between the lattice calculation, the experimental data and the PCAC relation of the nucleon axial form factors - axial and (induced)-pseudoscalar - has been understood as a systematic resulting from missing multihadron (nucleon and pions) excited states in the analysis. These low-lying excited states are hard to resolve in the conventional analysis. Fits to the temporal component...
Recent work in Euclidean dynamical triangulations (EDT) has provided compelling evidence for its viability as a formulation of quantum gravity. In particular the lattice value of the renormalized Newton's constant has been obtained by two distinct methods (the binding energy of scalar particles on the lattice, and comparison with the Hawking-Moss instanton). That these calculations yield...
Statistical modeling plays a key role in lattice field theory calculations. Examples including extracting masses from correlation functions or taking the chiral-continuum limit of a matrix element. We discuss the method of model averaging, a way to account for uncertainty due to model variations, from the perspective of Bayesian statistics. Statistical formulas are derived for model-averaged...
The light-cone definition of Parton Distribution Functions (PDFs) does not allow for a direct ab initio determination employing methods of Lattice QCD simulations that naturally take place in Euclidean spacetime. In this presentation we focus on pseudo-PDFs where the starting point is the equal time hadronic matrix element with the quark and anti-quark fields separated by a finite distance. We...
We present a new method to numerically investigate the gravitational collapse of a free, massless scalar quantum field in the semiclassical approximation from a spherically symmetric, coherent initial state. Numerical results are presented for a small ($r_s=3.5 l_p$) wave packet in the l=0 approximation. We observe evidence for the formation of a horizon and study various systematic effects...
In this talk, we discuss results for the Roberge Weiss (RW) phase transition at nonzero imaginary baryon and isospin chemical potentials, in the plane of temperature and quark masses. Our study focuses on the light tricritical endpoint which has already been used as a starting point for extrapolations aiming at the chiral limit at vanishing chemical potentials. In particular, we are interested...
We study the thermodynamic properties of QCD at nonzero isospin chemical potential using improved staggered quarks at physical quark masses. In particular, we will discuss the determination of the equation of state at zero and nonzero temperatures and show results towards the continuum limit. Based on the results for the isospin density $n_I$, the phase diagram in the $(n_I,T)$-plane will also...
The lattice formulation of finite-temperature field theory is readily extended,
via the Schwinger-Keldysh contour, to accomodate the definition of real-time
observables. Unfortunately, this extension also induces a maximally severe sign
problem, obstructing the computation of, for example, the shear viscosity. In
the large-N limit of certain field theories, including $O(N)$-symmetric...
If and how gauge theories thermalize is an unanswered question. Partly, this is due to the inability of lattice gauge theory (LGT) simulations to simulate out-of-equilibrium quantum dynamics on classical computers, but also due the difficulty of defining entanglement entropy in lattice gauge theories and finding schemes for its practical computation.
In this work, we study real-time...
Lattice QCD calculations of two-nucleon interactions have been underway for about a decade, but still haven't reached the pion mass regime necessary for matching onto effective field theories and extrapolating to the physical point. Furthermore, results from different methods, including the use of the Luscher formalism with different types of operators, as well as the HALQCD potential method,...
The relationship between finite volume multi-hadron energy levels and matrix elements and two particle scattering phase shifts and decays is well known, but the inclusion of long range interactions such as QED is non-trivial. Inclusion of QED is an important systematic error correction to K->\pi\pi decays. In this talk, we present a method of including a truncated, finite-range Coulomb...
We present an ab initio calculation of the individual up, down, and strange quark unpolarized, helicity, and transversity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of lattice QCD. We use a $N_f = 2 + 1 + 1$ gauge ensemble simulated with pion mass $M_\pi = 250$ MeV, $M_\pi L \approx 3.8$ and lattice...
According to perturbation theory predictions, QCD matter in the zero-temperature, high-density limits of QCD at nonzero isospin chemical potential is expected to be in a superfluid Bardeen-Cooper-Schrieffer (BCS) phase of $u$ and $\bar{d}$ Cooper pairs. It is also expected, on symmetry grounds, that such phase connects via an analytical crossover to the phase with Bose-Einstein condensation...
We compute a real-time inclusive scattering processes from the spectral function of a Euclidean two-point correlation function in the two-dimensional O(3) model. The intractable inverse problem is overcome using a recently-proposed algorithm to compute the desired spectral function smeared with a variety of finite-width kernels. Systematic errors due to finite volume, continuum limit, and...
Reduced staggered fermions afford a very economical lattice fermion formulation yielding just two Dirac fermions in the continuum limit. They have also been used to construct models capable of symmetric mass generation. However, generically they suffer from sign problems. We discuss an application of the tensor renormalization group, a sign problem free method, to such models. We make a...
In non-Hermitian random matrix theory there are three universality classes for local spectral correlations: the Ginibre class and the nonstandard classes AI$^\dagger$ and AII$^\dagger$. We show that the continuum Dirac operator in two-color QCD coupled to a chiral U(1) gauge field or an imaginary chiral chemical potential falls in class AI$^\dagger$ (AII$^\dagger$) for fermions in pseudoreal...
We present results of tensor network simulations of the three-dimensional O(2) model at nonzero chemical potential and temperature, which were computed using the higher order tensor renormalization group method. This also includes some enhancements to the method which take care of anisotropic tensors. Some special care was also taken to reduce the systematic error on the computation of the observables.
We study QCD at finite temperature in the presence of imaginary electric fields. In particular, we determine the electric susceptibility, the leading coefficient in the expansion of the QCD pressure in the imaginary field. Unlike for magnetic fields, at nonzero temperature this coefficient requires a non-trivial separation of genuine electric field-related effects and spurious effects related...
We present a calculation of lattice QCD non-local matrix elements that can be used to determine polarized gluon Ioffe-time distribution and the corresponding parton distribution function using QCD short distance factorization. We construct the nucleon interpolation fields using the distillation technique and flow the gauge fields using the gradient flow. Our calculation is performed on a $32^3...
L\"{u} scher method for two-particle scattering is a critical tool for
connecting finite-volume spectrum to infinite-volume scattering phaseshifts.
We numerically validate the quantization conditions up to partial waves l=4.
Various setups used in practice are considered: cubic or elongated lattices, rest or moving frames, unequal or equal masses, and integer or half-integer total...
We present our calculation of the unpolarized gluon parton distribution function (PDF) in the nucleon using the Pseudo-PDF technique on a $32^3 \times 64$ isotropic lattice with a pion mass of 358 MeV. The nucleon interpolating fields are reconstructed using distillation and we apply the sGEVP method to calculate the gluonic matrix elements. We smear the gauge fields using the gradient-flow to...
We discuss developments in calculating multi-hadron form-factors and transition processes via lattice QCD. Our primary tools are finite-volume scaling relations, which map spectra and matrix elements to the corresponding multi-hadron infinite-volume amplitudes. We focus on two hadron processes probed by an external current, and provide various checks on the finite-volume formalism in the...
It's well known that the deconfinement transition temperature for $SU(N_c)$ gauge theory is almost independent of $N_c$, and the transition is first order for $N_c \ge 3$. In the real world ($N_c=3$, light quarks) it is a crossover located far away from the pure gauge value. What happens if you keep the number of fermion flavors fixed ($N_f=2$) and vary the fermion mass and $N_c$? There are...
Abstract: The SU(3) Yang-Mills matrix model coupled to fundamental
fermions is an approximation of quantum chromodynamics (QCD) on a
3-sphere of radius R. The spectrum of this matrix model Hamiltonian
estimated using standard variational methods, and is analyzed in the
strong coupling limit. By employing a renormalization prescription to
determine the dependence of the Yang-Mills...
Quark confinement mechanism is one of unsolved important problems in QCD. In the dual Meissner picture of color confinement, it is considered that the color flux tube between static quarks is caused by the condensation of color magnetic monopoles in the QCD vacuum. In this talk, we show new results of the dual Meissner effect due to the violation of non-Abelian Bianchi identity corresponding...
We summarize the results of the recent work of calculating the $\pi\pi$ scattering phase shifts for both the s-wave I=0 and I=2 channels at 4 different energies around the kaon mass with physical quark mass and focus on three new topics presented in that work. (i) A determinant test that can be applied to multi-operator data at a single time separation to detect excited state contamination. ...
Lattices on Spherical Manifolds or on the cylindrical boundary of Anti-de-Sitter
space have the potential to explore non-perturbative conformal or near conformal
gauge theories for BSM studies for composite Higgs or Dark Matter. We report
on progress in the use of Quantum Finite Elements (QFE) to address renormalization on maximally symmetric spherical simplicial manifolds. The...
The dual superconductor picture is one of the most promising scenarios for quark confinement. To investigate this picture in a gauge-invariant manner, we have proposed a new formulation of Yang-Mills theory on the lattice, named the decomposition method, so that the so-called restricted field obtained from the gauge-covariant decomposition plays the dominant role in quark confinement. It was...
Instanton-dyons are topological solutions of YM equations at finite temperatures.
Their semiclassical ensembles were studied by a number of methods, including
direct Monte-Carlo simulation, for SU(2) and SU(3) theories, with and without fermions.
We present these results and compare them with those from lattice studies. We also
consider two types of QCD deformations. One is by adding...
We review some highlights of the centre vortex research programme conducted by the CSSM in SU(3) lattice gauge theory. Starting from the original Monte Carlo gauge fields, a vortex identification procedure yields vortex-removed and vortex-only backgrounds. The original, vortex-removed, and vortex-only ensembles are compared by examining a number of different quantities. The removal of vortices...
A variety of phenomena in the Standard Model and its extensions manifest in long-range processes involving on-shell multi-hadron intermediate states. Given recent algorithmic and conceptual progress, such processes are now realistic targets for lattice QCD. In this talk, I present a recently developed formalism that makes possible the determination of reactions of the form...
We present the necessity of counter terms for Quantum Finite Element (QFE) simulations of $\phi^4$ theory on non-trivial simplicial manifolds with semi-regular lattice spacing. In particular, by computing the local cut-off dependence of UV divergent diagrams we found that the symmetries of the continuum theory are restored for $\phi^4$ theory on the manifolds $\mathbb{S}^2$ and $\mathbb{R}...
The phase diagram of finite-density QCD is potentially quite complex. Like other lattice models with sign problems and generalized $\mathcal PT$ symmetry, equilibrium states of lattice QCD at finite density may be inhomogeneous, with commensurate and incommensurate patterned phases. The phase structures of such models are determined by a set of interwoven concepts: $\mathcal PT$ symmetry,...
We present the results that are necessary in the ongoing lattice calculations of the unpolarized and polarized gluon parton distribution functions (PDFs) within the pseudo-PDF approach. We give a classification of possible two-gluon correlator functions and identify those that contain the invariant amplitude determining the gluon PDF in the light-cone $z^2\to 0$ limit. One-loop calculations...
We study the phase structure of effective models of finite-density QCD using analytic and lattice simulation techniques developed for the study of non-Hermitian and $\mathcal{PT}$-symmetric QFTs. Finite-density QCD is symmetric under the combined operation of the charge and complex conjugation operators $\mathcal{CK}$, which falls into the class of so-called generalized $\mathcal{PT}$...
We explore holography with geometry fluctuation in the two-dimensional hyperbolic lattice. We present results on the behavior of the boundary-boundary correlation function of scalar fields propagating on discrete 2D random triangulations with the topology of a disk. We use a gravitational action that includes a curvature squared operator which favors a regular tessellation of hyperbolic space...
This presentation examines the centre-vortex structure of Monte-Carlo generated gauge-field configurations using modern visualisation techniques. This time, the manner in which light dynamical fermion degrees of freedom impact the centre-vortex structure is explored. Focusing on the thin vortices identified by plaquettes having a non-trivial centre phase, the vortex structure is illustrated...
There are a number of tetraquark channels for which some phenomenological models -- already constrained by the ordinary meson and baryon spectrum -- predict deep binding. We present results from our lattice calculations of doubly-charmed and bottom-charm channels where such predictions exist. Finding no evidence of deep binding, we can rule out those models, although this does not preclude the...
We present preliminary lattice calculations of strange and charm contributions to nucleon charges and moments. The scalar charge, axial charge, tensor charge, and unpolarized first moments are calculated on five clover-on-HISQ lattices covering three lattice spacings $a=\{0.06,0.09,0.12\}$~fm and three pion masses $M_\pi=\{310,220,130\}$~MeV. We renormalize the matrix elements with...
This presentation introduces new insights into the centre-vortex structure of lattice gauge fields, this time exploring the influence of dynamical fermions in the full-QCD vacuum. Calculations of both the Landau-gauge gluon propagator and the static quark potential reveal notable differences in the vortex phenomenology of pure-gauge and full-QCD simulations. Remarkably, configurations composed...
We consider a massive fermion system having a curved domain-wall
embedded in a square lattice.
As already reported in condensed matter physics, the massless chiral edge modes
appearing at the domain-wall feel "gravity" through the induced spin
connections.
In this work, we embed $S^1$ and $S^2$ domain-wall into Euclidean space
and show how the gravity is detected from the spectrum of...
We present a phase diagram study of the O(4) model as an effective
theory for 2-flavor QCD. Both theories perform spontaneous symmetry
breaking with isomorphic groups, which suggests that they
belong to the same universality class. Since we are interested
in high temperature, we further assume dimensional reduction
to the 3d O(4) model, which implies topological sectors.
As conjectured...
We present the first calculation within lattice QCD of excited light meson resonances with $J^{PC} = 1^{--}$, $2^{--}$ and $3^{--}$. Working with an exact SU(3) flavor symmetry, for the singlet representation of pseudoscalar-vector scattering, we find two $1^{--}$ resonances, a lighter broad state and a heavier narrow state, a broad $2^{--}$ resonance decaying in both $P$-- and $F$--waves, and...
The two-photon decay process ηc→2γ can provide an ideal testing ground for the understanding of nonperturbative nature of QCD. In this study, we propose a direct method to calculate the matrix element of a hadron decaying to two-photon. Various systematic effects are examined in this work. The method developed here can also be applied for other processes which involve the leptonic or radiative...
The gravitational form factors (GFFs) of hadrons are the form factors of the energy momentum tensor of QCD, which quantifies how the energy, spin and mechanical properties are distributed within hadrons and how they split between the quark and gluon degrees of freedom. We use the Belifante-Rosenfeld prescription in a Lattice QCD calculation with pion mass $m_{\pi} = 450 \; \text{MeV}$ to...
The important role of center vortices in dynamical chiral symmetry breaking and corresponding dynamical mass generation has been demonstrated in quenched studies of the Landau gauge quark propagator. We present the results of our investigation into the impact of center vortex removal on the Landau gauge quark propagator computed with overlap fermions on dynamical gauge fields. Upon removal of...
We analyze the chiral phase transition of the Nambu–Jona-Lasinio model in the cold and dense region on the lattice developing the Grassmann version of the anisotropic tensor renormalization group algorithm. The model is formulated with the Kogut–Susskind fermion action. We use the chiral condensate as an order parameter to investigate the restoration of the chiral symmetry. The first-order...
We investigate the distribution of energy-momentum tensor (EMT) around a static quark in the deconfined phase of SU(3) Yang-Mills theory. The EMT defined through the gradient-flow formalism is used for the numerical analysis of the EMT distribution around the Polyakov loop with the continuum extrapolation. Using EMT, one can study the mechanical distortion of the color gauge field induced by...
A novel method is proposed to determine the quark-diquark potential together with quark and diquark masses in the framework of Lattice Quantum Chromo Dynamics (LQCD). Treating a baryon as a quark-diquark bound state, we construct the corresponding two-body potential from the equal-time quark-diquark Nambu-Bethe-Salpeter (NBS) wave function by demanding it to satisfy the Schroedinger equation....
We study the nature of the phase transition at high temperature and high density in lattice gauge theories by focusing on the probability distribution function, which represents the probability of appearance of particle density in a heat bath. The probability distribution function is obtained by constructing a canonical partition function by fixing the number of particles from the grand...
We make an analysis of the two-dimensional U(1) lattice gauge theory with a θ term by using the tensor renormalization group.
Our numerical result for the free energy shows good consistency with the exact one at finite coupling constant. The topological charge density generates a finite gap at θ=π toward the thermodynamic limit.
In addition finite size scaling analysis of the topological...
We present the first Lattice QCD calculation of the quark and gluon trace anomaly contributions to the hadron masses, using the overlap fermion on the 2+1 flavor dynamical Domain wall quark ensemble. The result shows that the gluon trace anomaly contributes to most of the nucleon mass, and the contribution in the pion state is smaller than that in others.
Removing ultraviolet noise from the gauge fields is necessary for glueball spectroscopy in lattice QCD. It is known that the Yang-Mills gradient flow method is an alternative approach instead of smearing or fuzzing of the links in various aspects. In this talk, we study the application of the gradient flow technique to the construction of the extended glueball operators. We find that a simple...
We study chirality of staggered quarks on the Dirac eigenvalue spectrum using deep learning techniques. The theory expects a characteristic pattern (we call it "leakage pattern") in the matrix elements of the chirality operator sandwiched between two eigenstates of staggered Dirac operator. Deep learning analysis gives 99.4(24)% accuracy per a single normal gauge configuration and 0.998 AUC...
We investigate the metal-insulator transition of the (1+1)-dimensional Hubbard model in the path-integral formalism with the tensor renormalization group method. The critical chemical potential $\mu_{\rm c}$ and the critical exponent $\nu$ are determined from the $\mu$ dependence of the electron density in the thermodynamic and zero-temperature limit. Our results for $\mu_{\rm c}$ and $\nu$...
As a new algorithm towards solving the sign problem, we propose the "worldvolume tempered Lefschetz thimble method" (WV-TLTM) [1]. In this algorithm, we make hybrid Monte Carlo updates on a continuum set of integration surfaces foliated by the antiholomorphic gradient flow ("the worldvolume of the integration surface"). This algorithm is an extension of the tempered Lefschetz thimble method...
Attendees should create a DevCloud account using below link and event code before the session:
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The session includes a giveaway of 10 Intel GPU developer platforms.
Join our virtual workshop on Essentials of Data Parallel C++ to learn about oneAPI which aims to provide a unified, cross-industry,...
In complex Langevin simulations, the insufficient decay of the probability density near infinity leads to boundary terms that spoil the formal argument for correctness. We present a formulation of this term that is cheaply measurable in lattice models, and in principle allows also the direct estimation of the systematic error of the CL method. Results for various lattice models from XY model...
I outline the simulation of lattice QCD with $N_f=2+1+1$ optimal domain-wall quarks at the physical point, on the $64^3 \times (6,8,10,12,16,20) $ lattices, for three lattice spacings $a \sim 0.064-0.075$ fm. The quark masses and lattice spacings are determined at the zero temperature on the $64^4$ lattice. The topological susceptibility of each gauge ensemble is measured by the Wilson flow....
The rho meson is the lightest strongly decaying particle and also the simplest spin-1 meson, which allows for the study of polarisation dependent structure functions that are not present in the spin-1/2 case. Its unstable nature complicates the analysis of its structure, both on the lattice and in experiment. However, it allows us to study the interplay between hadron polarization and parton...
We present a comparison of existing experimental data for the radiative leptonic decays $P \to \ell \nu_\ell \gamma$, where $P=K$ or $\pi$ and $\ell = e$ or $\mu$, from the KLOE, PIBETA, E787, ISTRA+ and OKA collaborations performed in Ref. [1] using the theoretical predictions based on the recent non-perturbative determinations of the structure-dependent vector and axial-vector form factors,...
The complex Langevin method is a general method to treat systems with
complex action, such as QCD at finite density. The formal justification
relies on the absence of certain boundary terms, both at infinity and at
the unavoidable poles of the drift force. In this talk I focus on the
boundary terms at poles for simple models, which so far have not been
discussed in detail. The main result...
In recent years many candidates for states beyond the most simple realization of the quark model were found in various experiments around the world. However, so far no consensus exists on their structure, although there is strong evidence that at least some of those are dynamically generated from meson-meson interactions.
We provide an important missing piece from the theoretical side to...
We provide a first study of Mellin moments of double parton distributions (DPDs) in the nucleon on the lattice, where we consider several combinations of quark flavors and polarizations. These are accessible through two-current correlations, which can be obtained by evaluating four-point functions. In this context we consider all possible Wick contractions, where for almost all of them...
The $K\rightarrow\pi\ell^{+}\ell^{-}$ decay is a flavor changing neutral current process which is forbidden at tree level in the Standard Model and thus may be sensitive to potential new physics. This decay is currently being measured at the NA62 experiment in CERN and its form factor is known only through experimental results. I will discuss the ongoing lattice QCD calculation of the $q^2=0$...
Near the second order phase transition point, QCD with two flavours of massless quarks can be approximated by an $O(4)$ model, where a symmetry breaking external field $H$ can be added to play the role of quark mass. The Lee-Yang theorem states that the equation of state in this model has a branch cut along the imaginary $H$ axis for $|\text{Im}[H]|>H_c$, where $H_c$ indicates a second order...
The lightest scalar charm-light $D_0^\star$ and charm-strange $D_{s0}^\star$ mesons have been puzzling in that experiments have found them at approximately the same mass. This is in contrast with the quark-model prediction. For the first time, we map out the energy dependence of the elastic Isospin-1/2 $D\pi$ scattering amplitude and find a complex $D_0^\star$ resonance pole, using Lattice QCD...
We study, with lattice QCD, the leptonic decays of pseudoscalar mesons of the type $P^+\to l^+\,\nu_l\,l'^+\,l'^-$. These processes are mediated by the emission of a virtual photon which also interacts with the hadronic structure of the pseudoscalar meson $P^+$, giving rise to relevant structure-dependent corrections. They are very suppressed processes, which thus provide an excellent test for...
We compare two frequently discussed competing structures for a stable $\bar{b} \bar{b} u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$ by considering meson-meson as well as diquark-antidiquark creation operators. We treat the heavy antiquarks as static with fixed positions and find diquark-antidiquark dominance for $\bar{b} \bar{b}$ separations $r < 0.25 \, \text{fm}$, while for $r >...
In this talk we present the novel relations between the quark mass derivatives [$\partial^{n}\rho(\lambda,m_l)/\partial m_{l}^{n}$] of the Dirac eigenvalue spectrum and the $(n+1)$-point correlations among the eigenvalues. Using these relations we present lattice QCD results for $\partial^{n}\rho(\lambda,m_l)/\partial m_{l}^{n}$ ($n=1, 2, 3$) for $m_l$ corresponding to pion masses...
We study a gauge-invariant renormalization scheme (GIRS) for composite operators, regularized on the lattice, by extending the coordinate space (X-space) scheme proposed some years ago. In this scheme, Green's functions of products of gauge-invariant operators located at different spacetime points are considered. Due to the gauge-invariant nature of GIRS, gauge fixing is not needed in the...
We present a high-precision Monte Carlo study of the $O(3)$ spin theory on the lattice in $D=4$ dimensions. This model exhibits interesting dynamical features, in particular in the broken-symmetry phase, where suitable boundary conditions can be used to enforce monopole-like topological excitations. We investigate the Euclidean time propagation and the features of these excitations close to...
The rare hyperon decay $\Sigma^+ \to p \ell^+ \ell^-$ is an $s \to d$ flavour changing neutral current process that has been recently measured by the LHCb experiment with plans to improve this measurement in the future. This has prompted a need for an improved Standard Model prediction of the branching fraction of this decay.
We present our theoretical approach and progress towards an...
We present preliminary HPQCD results for $B \to K$ form factors $f_{0,+,T\,}(q^2)$ using the HISQ action for all valence quarks on the MILC $N_f = 2 + 1 + 1$ gauge field ensembles. The ensembles used cover five lattice spacings, include the physical pion mass, and span a range of heavy quark masses from $m_c$ to near $m_b$. Our ''heavy-HISQ'' approach allows us to map form factor heavy-quark...
We study $I = 0$ quarkonium resonances decaying into pairs of heavy-light mesons using static-static-light-light potentials from lattice QCD. To this end, we solve a coupled channel Schrödinger equation with a confined quarkonium channel and channels with a heavy-light meson pair to compute phase shifts and t-matrix poles for the lightest decay channel. Additionally, we study the quark...
In this talk I present a recent proposal for a novel action for lattice gauge theory for finite systems, which accommodates non-periodic boundary conditions [1]. Drawing on the summation-by-parts formulation of finite differences and finite volume strategies of computational electrodynamics, an action is constructed that implements the proper integral form of Gauss' law and exhibits an...
Dirac Eigenvalue spectrum $\rho$ and its derivatives with respect to quark mass are useful quantities to study the microscopic origin of the chiral symmetry breaking in QCD. It has been proposed in Ref.[1] that the n-th order derivative of Dirac eigenvalue spectrum with respect to quark mass $\partial^n\rho/\partial m^n$ is connected to the (n+1)-point correlation function among Dirac...
The pseudo-distribution formalism is one such methodology capable of illuminating the collinear structure of hadrons from matrix elements of suitably constructed space-like operators calculated using lattice QCD. Looking more closely at the unpolarized nucleon PDF calculation of the HadStruc collaboration, the improved statistical quality of the computed Ioffe-time pseudo-distributions opens...
I will discuss some recent lattice QCD calculations of $DK$ and $D\bar{K}$ scattering, relevant for the enigmatic $D^\ast_{s0}(2317)$, with light-quark masses corresponding to $m_\pi = 239$ MeV and $m_\pi = 391$ MeV. The S-waves contain interesting features including a near-threshold $J^P = 0^+$ bound state in isospin-0 $DK$, corresponding to the $D^\ast_{s0}(2317)$, with an effect that is...
We are presenting our ongoing Lattice QCD study on $B - \bar{B}$ mixing on several RBC/UKQCD and JLQCD ensembles with 2+1 dynamical-flavour domain wall fermions, with a range of inverse lattice spacings from 1.7 to 4.5 GeV and including physical-pion-mass ensembles. We compare various different fitting strategies to extract bag parameters $B_{B_d}$ and $B_{B_s}$ both for the standard-model...
The Renormalization Group (RG) is one of the central and modern techniques in quantum field theory. Indeed, quantum field theories can be understood as flows between fixed points, representing Conformal Field Theories (CFT's), of the RG. Hence, the search and classification of yet unknown non-trivial CFT's is a legitimate endeavor. Analytical considerations point to the existence of such a...
Calculating the partonic structure of hadrons from lattice QCD has attracted a lot of interest in the past few years, and now has moved to a stage which calls for precision. In this talk, I'll discuss some important steps towards such precision calculations.
We consider the role that gauge symmetry breaking terms play on the continuum limit of gauge theories in three dimensions.
As a paradigmatic example we consider scalar electrodynamics in which $N_f$ complex scalar fields interact with a U(1) gauge field. We discuss under which conditions a mass term destabilizes the critical behavior (continuum limit) of the gauge-invariant theory and the...
We report our effort on calculating the neutron electric dipole moment (EDM) induced by the theta term using overlap fermions. Three 2+1-flavor RBC/UKQCD domain wall lattices with pion mass ranging from ~300 to ~500 MeV are utilized and on each gauge ensemble we use 3 partially-quenched valence pion masses. Lattice chiral fermions are essential in the calculation, which guarantees a correct...
We present the next-to-next-to-leading order (NNLO) calculation of quark quasiparton distribution functions (PDFs) in the large momentum effective theory. The nontrivial factorization at this order is established explicitly and the full analytic matching coefficients between the quasidistribution and the light-cone distribution are derived. In the end we get the PDFs within our NNLO matching...
We study the charmonium spectrum on an ensemble with two heavy dynamical quarks with a mass at half the physical charm quark mass. Operators for different quantum numbers are used in the framework of distillation with different smearing profiles to increase the overlap with ground and excited states. The use of exact distillation, large statistics and the absence of light quarks gives robust...
We present preliminary lattice results for the topological susceptibility in high-temperature $N_f=2+1$ QCD obtained discretizing this observable via spectral projectors on eigenmodes of the staggered operator, and we compare them with those obtained with the standard gluonic definition.
The adoption of the spectral discretization is motivated by the large lattice artifacts affecting the...
We investigate doubly heavy tetraquarks with quark structure $ \bar{Q}\bar{Q}'qq'$ in full lattice QCD using the NRQCD formalism for bottom quarks. We focus mainly on bound states in systems with two heavy antiquarks $ \bar{b}\bar{b} $ and $ \bar{b}\bar{c} $ in the present of light quarks $q \in \{u,d,s\} $.
Universal features of second order phase phase transitions can be investigated by studying the phi-to-the-fourth field theory with the corresponding global symmetry breaking pattern. When gauge symmetries are present, the same technique is usually applied to a gauge invariant order parameter field, as in the Pisarski-Wilczek analysis of the QCD chiral phase transition. Gauge fields are thus...
I show that a finite density of near-zero localised Dirac modes can lead to the disappearance of the massless excitations predicted by the finite-temperature version of Goldstone's theorem in the chirally-broken phase of a gauge theory.
The nucleon tensor charge, g$_T$, is an important quantity in the search for beyond the Standard Model tensor interactions in neutron and nuclear $\beta$-decays as well as the contribution of the quark electric dipole moment (EDM) to the neutron EDM. We present results from the QCDSF, UKQCD and the CSSM collaboration for the tensor charge, $g_T$, using lattice QCD methods and the...
The transverse momentum dependent soft function introduced to describe soft-gluon effects plays an important role in QCD factorization. We present a lattice QCD study on this function by simulating pion matrix element and quasi TMD wave function using the large momentum effective theory. The momenta we adopted are up to $3 $ GeV. Various systematic effects are examined in our study.
We address the interplay between local and global symmetries by analyzing the continuum limit of two-dimensional multicomponent scalar lattice gauge theories, endowed by non-abelian local and global invariance. These theories are asymptotically free. By exploiting Monte Carlo simulations and Finite-Size Scaling techniques, we thus provide numerical results concerning the universal behavior of...
We present lattice results for the non-perturbative Collins-Soper (CS) kernel, which describes the energy-dependence of transverse momentum-dependent parton distributions (TMDs). The CS kernel is extracted from the ratios of first Mellin moments of quasi-TMDs evaluated at different nucleon momenta.The analysis is done with dynamical $N_f=2+1$ clover fermions for the CLS ensemble H101...
There are several unexplained resonances in the charmonium sector. To this end we present a study of the masses and decay constants of the lightest multiplet of charmonium-like hybrid mesons. We obtain precise measurements through the use of a variational basis and a large number of configurations at three lattice spacings. We use staggered fermion operators and our configurations are...
It is known that the deconfining transition of QCD is accompanied by the
appearance of localized eigenmodes at the low end of the Dirac spectrum. In
the quenched case localization appears exactly at the critical temperatura of
deconfinement. In the present work, using quenched simulations exactly at the
critical temperature we show that the localization properties of low Dirac
modes...
In QCD there is the possibility of strong CP violation arising from a nonvanishing vacuum angle $\theta$, which would result in an electric dipole moment $d_n$ of the neutron. Recently it has been shown that QCD undergoes a deconfinement phase transition at finite values of $\theta$ due to long-distance vacuum effects, which rules out any CP violation at the hadronic level, thus solving the...
One consequence of the recently developed effective number theory, designed to count objects with probabilities, is that it leads to a well-defined concept of effective dimension. Due to the additivity of effective numbers, the latter is a measure-based construct extending the Hausdorff/Minkowski-like notion of dimension for fixed sets (with metric) to the stochastic domain. Both IR...
We use the two-dimensional Schwinger model to investigate how lattice fermion operators perceive the global topological charge $q\in\mathbf{Z}$ of the gauge background. After a warm-up part devoted to Wilson and staggered fermions, we consider Karsten-Wilczek and Borici-Creutz fermions, which are in the class of minimally doubled lattice fermion actions. The focus is on the eigenvalue spectrum...
We will present results on the neutron electric dipole moment $\vert \vec{d}_N\vert$ using an ensemble of $N_f=2+1+1$ twisted mass clover-improved fermions with lattice spacing of $a \simeq 0.08 \ {\rm fm}$ and physical pion mass ($m_{\pi} \simeq 139 \ {\rm MeV}$). The approach followed in this work is to compute the $CP$-odd electromagnetic form factor $F_3(Q^2 \to 0)$ by expanding the...
In 2011, Belle discovered two $Z_b^+$ hadrons with quark content $\bar{b}b\bar{d}u$. Lattice study of hadrons with this quark content is challenging because they can decay to two $B$-mesons and also to a bottomonium and a light meson, leading to a large number of decay channels. We present a lattice study of the $\bar{b}b\bar{d}u$ system with the static bottom quarks. Only the channel that...
We show that the transverse momentum dependent parton distribution functions
(TMDPDFs), important for understanding 3D hadron structure and describing
high-energy experiments, can be formulated in the framework of the
large-momentum effective theory(LaMET). We show that the quasi-TMDPDFs,
calculable on lattice, factorize at large momentum limit into physical-TMDPDFs
and reduced soft...
The bosonization procedure for Majorana modes based on Clifford algebra-valued degrees of freedom, valid for arbitrary lattices, will be summarized. In the case of honeycomb geometry the Kitaev model emerges. The role of boundary effects and edge states will be discussed.
The transverse-momentum-dependent (TMD) soft function is a key ingredient in QCD factorization of Drell-Yan and other processes with relatively small transverse momentum. We present a lattice QCD study of this function at moderately large rapidity on a 2+1 flavor CLS dynamic ensemble with a = 0.098 fm. We extract the rapidity-independent (or intrinsic) part of the soft function through a...
We will show mesonic ground masses at increasing temperatures for different flavour structures and operators. The mass extraction is carried out using a fitting procedure on anisotropic thermal correlation functions. We use FASTSUM collaboration thermal ensembles corresponding to an anisotropy of $\xi = 3.5 = a_\tau / a_s$.
Using the meson masses as a function of the temperature, we aim to...
Lattice Quantum Chromodynamics (LQCD) provides the most direct probe into sources of CP-violation. These sources assume an effective form in higher-dimensional local operators built from QCD fields. Unfortunately, the operators mix with lower-dimensional operators under renormalization, introducing power divergences in the lattice spacing which inhibit a smooth continuum limit. The gradient...
We compute flavor non-singlet meson screening masses in the chiral limit of QCD with $N_f=3$ quarks. The calculation is
carried out at 11 temperatures covering from $T\approx 1$ GeV up to the electroweak scale. For each temperature we simulated
4 different lattice spacings, so as to be able to perform the continuum limit extrapolation with confidence at a few permille-accuracy. The...
The euclidean representation of a newly proposed spin system, which is equivalent to a single Majorana fermion in 2+1 dimensions, is derived. The unconstrained euclidean system reveals a mild sign problem which is quantitatively studied. Implementing constraints without breaking positivity will be shortly outlined.
We’ll present the first lattice QCD calculation of transverse momentum dependence wave function of pion using large momentum effective theory. We use the clover fermion action on three ensembles with $2+1+1$ flavors of highly improved staggered quarks (HISQ) action, generated by MILC collaboration, at pion mass $670MeV$ and $0.12 fm$ lattice spacing, choose three different hadron momenta...
The quark-chromo electric dipole moment (qCEDM) operator is one of the possible beyond-the-standard-model (BSM) contributions to the electric dipole moment (EDM). Power divergences of lower dimensional operators are introduced to the qCEDM operator by operator mixing. We compute non-perturbatively the qCEDM power divergence coefficient with the gradient flow, allowing us to control the power...
Preliminary results for the spectra of excited and exotic $B$, $B_s$ and $B_c$ mesons are presented. The calculation on a dynamical anisotropic lattice employs distillation, enabling a large basis of interpolating operators including those proportional to the gluonic field strength which are relevant for hybrid states. A comparison with a similar calculation of $D$ and $D_s$ mesons is made.
We will discuss the determination of the properties of heavyonium mesons in lattice QCD + quenched QED, using the HISQ action on gluon field configurations that include 2+1+1 flavours of sea quarks and with lattice spacing values going down to 0.03 fm. Results include values for the bottomonium hyperfine splitting and Upsilon and eta_b decay constants, for comparison to our earlier results for...
I will present new results from investigations of lattice supersymmetric Yang--Mills theories in three and four dimensions. The fermion action of these theories involves a Pfaffian that may be complex. A first analysis of the complex phase of the Pfaffian, $\left\langle e^{i\phi} \right\rangle$, for the 3D theory with maximal supersymmetry (16 supercharges) reveals very small fluctuations...
In this work we study the renormalization of the SUSY Noether current in Supersymmetric $\cal{N} =$ 1 Yang-Mills (SYM) theory on the lattice. In particular, we study the mixing of the current with all other compatible operators of dimension 7/2 and 5/2, leading from the lattice-regularized to the $\overline{\rm{MS}}$-renormalized operator basis. We perform our task in two ways:
(a) We...
I present GPT (https://github.com/lehner/gpt): a new Python measurement toolkit built on Grid data parallelism (MPI, OpenMP, SIMD, and SIMT). It provides a physics library for lattice QCD and related theories as well as a QIS module including a digital quantum computing simulator.
A lot of progress has been made in the determination of nucleon sigma terms. In this work we consider the sigma terms of the other octet baryons as well. These are determined on CLS gauge field ensembles employing the Lüscher-Weisz gluon action and the Sheikholeslami-Wohlert fermion action with $N_\mathrm{f} = 2 + 1$ . The ensembles have pion masses ranging from ${410}\,\mathrm{MeV}$ down to...
In lattice quantum chromodynamics with chiral fermions we want to solve linear systems which are chiral and dense discretizations of the Dirac operator, or the overlap operator. For this purpose, we use the equivalence of the overlap operator with the truncated overlap operator, which is a five dimensional formulation of the same theory. The coarsening is performed along the fifth dimension...
We developed a new production code for lattice gauge theory in Julia language. Julia language has developed quickly since 2012, and it is used for many of calculations in condensed matter physics. This code has compatible speed with a fortran code, ``Lattice Took Kit'', and enables us to perform (R)HMC with the staggered and Wilson fermions with stout smearing for SU(N) generic action and...
Recent FPGA accelerator cards promise large acceleration factors for some specific computational tasks. In the context of Lattice QCD calculations, we investigate the possible gain of moving the SU(3) gauge field smearing routine to such accelerators. We study Xilinx Alveo U280 cards in conjunction with Vitis high-level synthesis framework. We discuss the possible pros and cons of such...
We report recent progress in determining $\varepsilon_K$, the indirect
CP violation parameter in the neutral kaon system, calculated using
lattice QCD inputs including $\hat{B}_K$, $\xi_0$, $\xi_2$,
$|V_{us}|$, $|V_{cb}|$, and $m_c(m_c)$.
The mass shifts for two-fermion bound and scattering P-wave states subject to the long-range interactions due to QED in the non-relativistic regime in refs. [1, 2] are presented. Introducing a short range force coupling the spinless fermions to one unit of angular momentum in the framework of pionless EFT, we rst report the two-body scattering amplitudes with Coulomb corrections in the...
The order of the chiral phase transition of lattice QCD with staggered fermions is known to depend on the quark masses, the number of flavours and the lattice spacing. Studies in the literature show a weakening of the $N_f=3,4$ first-order transitions with decreasing lattice spacing. Here we
investigate what happens when lattices are made coarser, in order to establish contact to the strong...
In the early days of QCD, the axial $U(1)$ anomaly was considered to trigger the breaking of the $SU(2)_L\times SU(2)_R$ symmetry through topological excitations of gluon fields. However, it has been a challenge for lattice QCD to quantify the effect. In this work, we simulate QCD at high temperatures with the overlap Dirac operator. The exact chiral symmetry enables us to separate the axial...
We study latent heat and the pressure gap between the hot and cold phases at the first-order deconfining phase transition temperature of the SU(3) Yang–Mills theory. Performing simulations on lattices with various spatial volumes and lattice spacings, we calculate the gaps of the energy density and pressure using the small flow-time expansion (SFtX) method. We find that the latent heat...
We investigate the temperature and density dependence of the color flux tube structure of dense two-color QCD with Nf=2 Wilson fermions by using a lattice simulation. From Refs. [1] and [2], we have already clarified the rich phase structure in the low temperature region, including the hadronic and superfluid phases. In this study we measure the quark-antiquark potential and color flux tube...
We introduce a new non-perturbative method to tune the parameters of the Columbia formulation of an anisotropic, clover-improved relativistic heavy-quark (RHQ) action.
By making use of suitable observables which can be computed at a sequence of heavy-quark mass values, employing an $O(a)$-improved discretized action with domain-wall chiral fermion, and safely interpolated between the...
We present the application of a Wang-Landau type algorithm to a pure-gauge SU(4) model on the lattice, with the aim to calculate the gravitational wave signature of the SU(4) pure-gauge content of a composite Dark Matter model.
Due to the first order phase transition of the SU(4) model, two phases coexist at the critical temperature and for larger lattice sizes the chances of tunnelling...
Nucleon matrix elements are some of the most expensive quantities to calculate within the framework of lattice QCD simulations, as they involve the computation of nucleon three-point correlation functions. Nucleon three-point correlation functions need additional quark propagators compared to two-point correlation functions, and suffer from exponentially worsening signal-to-noise ratios as...
We perform a lattice study of the phase transition in the SU(2) Georgi-Glashow model in three dimensions, where the symmetry is broken to U(1) and a photon-like state appears. Motivated by studies of the QCD instanton, we use gradient flow to renormalise the monopole density and study the role of monopoles in the phase transition. We also use modern techniques to measure the mass of the...
We study a hybrid stochastic method for the tensor renormalization group
(TRG) approach.
The TRG is known as a powerful tool to study the many-body systems and
quantum field theory on the lattice.
It is based on a low-rank approximation of the tensor using the
truncated singular value decomposition (SVD),
whose computational cost significantly increases as the bond dimension
increases,...
SU(2) gauge theory with $N_f=24$ massless fundamental fermions is trivial: in the UV it has a Landau pole and in the IR it becomes free. At non-zero fermion mass the IR behaviour is expected to change: as the fermions decouple at sufficiently low energies, the theory reduces to pure gauge SU(2) and is therefore confining. We measure the evolution of the coupling constant with the gradient...
The recent experimental result for the muon’s anomalous magnetic
moment from Fermilab motivates the reduction of the errors on lattice
QCD calculations of the leading order hadronic contribution. All of our
calculations use the highly-improved staggered quark (HISQ)
formulation. The gauge configurations are generated with four flavors
of HISQ sea quarks with physical sea-quark masses....
An important aspect to consider in practical applications of quantum computing
is the computational cost of a quantum state preparation. Quantum adiabatic evolution is a possible technique based on the slow time evolution of the Hamiltonian from a simple one to the target one. A different approach is the so-called Rodeo algorithm, where stochastically, and in a recursive manner, all states...
We present the results on topological susceptibility and chiral observables in $N_f = 2 +1 + 1$ QCD for temperature range $120 < T < 600$ MeV. The lattice simulations are performed with Wilson twisted mass fermions at physical pion, strange and charm masses. In high-$T$ region the chiral observables are shown to follow leading order Griffith analyticity regardless the critical behaviour, and...
Recently, Feynman-Hellmann methods have been used to calculate four-point functions in lattice QCD, specifically the forward and off-forward Compton amplitudes. However, these calculations are subject to discretisation artifacts from where the two currents are inserted on the same time slice. Here, we discuss the effects of these temporal contact terms, especially their contribution to the...
Lattice calculations of hadronic observables are aggravated by short-distance fluctuations. The gradient flow, which can be viewed as a particular realisation of the coarse-graining step of momentum space RG transformations, proves a powerful tool for evolving the lattice gauge field to successively longer length scales for any initial coupling. Already at small flow times we find the...
The lattice community, and more widely the physics community, has a long track record of using and even building advanced Statistical & Machine Learning tools (e.g. HMC). On the other hand, the Machine Learning, and specifically the Deep Learning, community has itself been seeking inspiration from Physics. Geometry and symmetries are inspiring many ML papers and research directions. Those...
Using variational methods for QFT at strong coupling is an ancient dream with multiple concrete approaches. We discuss recent work on a particular approach, Lightcone Conformal Truncation, that uses lightcone quantization in infinite volume and a truncated Hilbert space motivated by the conformal symmetry of an ultraviolet fixed point at the upper end of an RG flow containing the QFT of interest.
The Variational Quantum Eigensolver (VQE) is a hybrid quantum-classical algorithm used to find the spectrum of a Hamiltonian using the variational method. In particular, this procedure can be used to study LGT in the Hamiltonian formulation. Bayesian Optimization (BO) based on Gaussian Process Regression (GPR) is a powerful algorithm for finding the global minimum of the energy with a very low...
The current precision reached by lattice QCD calculations
of low-energy hadronic observables, requires not only the introduction
of electromagnetic corrections, but also a control over all the potential
systematic uncertainties introduced by the lattice version of QED.
Introducing a massive photon as an infrared regulator in lattice QED, provides a
well defined theory, dubbed...
In recent years many QCD observables have reached (sub-)percent level precision. At this level strong ($m_u \neq m_d$) and weak (charges of up, down and strange) isospin breaking effects have to be accounted for. Different methods exist to include QED into lattice QCD simulations. In massive QED (QEDm) the photon is given a mass $m_\gamma$, allowing for a local formulation of QED on the...
Quantum computing allows for the study of real-time dynamics of non-perturbative quantum field theories while avoiding the sign problem in conventional lattice approaches. Current and near-future quantum devices are severely limited by noise, making investigations of simple low-dimensional lattice systems ideal testbeds for algorithm development. Considering simple supersymmetric systems,...
In this report, we present our results on the lattice study of the EoS of dense
QCD in an external magnetic field. The simulations are performed with
$N_f = 2+1$ rooted dynamical staggered quarks at the physical point.
Finite density is introduced through the imaginary chemical potentials
$\mu_u=\mu_d=\mu_I$, $\mu_s=0$. The EoS is obtained as series with respect
to $\mu$ up to $\mu^6$...
In this talk, we will be looking at quantum circuits comprising parametric gates and analyze their expressivity in terms of the space of states that can be generated by a given circuit. In particular, we will be considering parametric quantum circuits (PQCs) for use in variational quantum simulations (VQS). In such a setting, the design of PQCs is subject to two competing drivers. On one hand,...
We present HotQCD's software suite for performing lattice QCD calculations on GPUs. Started in late 2017 and intended as a full replacement of the previous single GPU lattice QCD Code used by the HotQCD collaboration, our software suite has been developed into an extensive toolkit for lattice QCD calculations distributed on multiple GPUs over many compute nodes. The code is built on C++, CUDA...
In this work we study the properties of $N_f=2+1$ QCD in the presence of a constant background magnetic field, up to unexplored large values of $eB$, by means of lattice Monte Carlo simulations. We investigate the string tension and its asymmetry via the study of the static quark-antiquark potential and of the color flux tube. Moreover, we present preliminary results regarding the QCD phase...
We present our progress in the non-perturbative $O(a)$ improvement and renormalisation of quark operators in three-flavour lattice QCD with Wilson-clover fermions. We employ the chirally rotated Schroedinger functional scheme in finite volumes. Our calculations cover both weak- and strong-coupling regions for the RG-running, where step scaling functions are computed.
In this contribution we announce the formation of a new initiative to study Stabilised Wilson Fermions (SWF). They are an interesting new avenue for QCD calculations with Wilson fermions and we report results on our continued study of this framework: Tuning the clover improvement coefficient we extend the reach of lattice spacings to $a=0.055,~0.064,~0.080,~0.094,~0.12\,$fm. We further tune...
We have recently performed a determination of the charm quark mass on $N_f = 2+1$ CLS ensembles of non-perturbatively improved Wilson fermions. The extrapolation to the chiral and continuum limits is performed using 5 lattice spacings ranging roughly from 0.09 down to 0.04 fm and pion masses from 420 MeV to 130 MeV. The spatial extent of the ensembles is generally at least $4 / M_\pi$. We will...
We present preliminary results of lattice QCD simulations with dynamical light and strange quarks, all flavors defined using Stabilised Wilson Fermions (SWF). The ensembles are tuned, see the preceding talk by A. Francis, at the flavor symmetric point $m_\pi=m_K=412$ MeV and the physical point is reached keeping fixed the trace of the quark mass matrix. We show a first determination of the...
We reformulate the continuous space Schrödinger equation in terms of spin Hamiltonians. For the kinetic energy operator, the critical concept facilitating the reduction in model complexity is the idea of position encoding. Binary encoding of position produces a Heisenberg-like model and yields exponential improvement in space complexity when compared to classical computing. Encoding with a...
In non-central heavy-ion collisions, the magnetic fields generated are stronger than any ground-based experiments, reaching magnitudes comparable to the strong scale and being highly non-uniform. To study such extreme conditions, we simulate the theory of strong interactions at finite temperature on the lattice, with staggered fermions and an inhomogeneous magnetic background. Just as in the...
We report on the progress made on the QDP-JIT library which acts as a drop-in replacement for the QDP++ library which Chroma builds upon. QDP-JIT now targets NVIDIA and AMD GPU machines, like the upcoming Frontier supercomputer, Summit or the new USQCD machine with AMD GPUs at Jefferson Lab. Our new implementation aims to add one missing feature of QDP++: performance.
We use the original...
We provide a modification to the textbook's quantum phase estimation algorithm (QPEA) inspired on classical windowing methods for spectral density estimation. From this modification we obtain an upper bound in the cost that implies a cubic improvement with respect to the algorithm's error rate. Numerical evaluation of the costs also demonstrate an improvement. Moreover, with similar...
I will describe the latest dynamical DWF ensemble generation efforts by RBC/UKQCD collaboration, focusing on 96^3x192x12, a ~ 0.07fm, 2+1 flavor ensemble with Iwasaki gauge action at physical point, running on summit machine at Oak Ridge National Laboratory. Basic properties of the ensemble as well as some details of the algorithmic improvements will be given.
Scalar $\phi^4$ theory in three dimensions with fields in the adjoint of $SU(N)$ is of interest as holographically dual to a model for inflationary cosmology. The theory is perturbatively IR divergent but it was proposed in the past that its dimensionful coupling constant plays the role of the IR regulator nonperturbatively. Using a combination of Markov-Chain-Monte-Carlo simulations of the...
In this talk, we present a model-independent calculation of the $x$-dependence of pion valence PDF with the large-momentum effective theory approach. In this calculation we adopt the most up-to-date theoretical developments on the systematic corrections, which include the hybrid renormalization scheme that rigorously renormalizes the lattice matrix elements at both short and long distances, as...
In holographic cosmology, the dual theory may be described by a family of super-renormalisable QFTs in 3 dimensions. In order to obtain cosmological observables, correlators in the massless regime of this QFT are obtained via lattice field theory. Previous work has focused on scalar $\phi^4$ matrix theories in the adjoint representation of SU(N). In this work we present a preliminary...
A long standing problem associated with performing lattice gauge theory calculations on GPU hardware is latency for both global memory transfers and MPI data transfers. Mitigating these latencies with data compression techniques can vastly improve the performance of solvers and help to combat strong scaling. In this talk we discuss a new gauge field compression technique in which the SU(N)...
We extend our study of the static potential in $N_f$=2+1 QCD to determine its quark mass dependence. We use a set of CLS (Coordinated Lattice Simulations) ensembles at a lattice spacing a=0.064 fm along a chiral trajectory of constant sum of the bare quark masses. The pion masses range from $m_\pi$=420 MeV at the symmetric point down to $m_\pi$=200 MeV. We use a model to parametrize the lowest...
We study pion valence structure from lattice QCD using three mixed action ensambles including a physical pion mass with fine lattice spacings of a = 0.04, 0.06 and 0.076 fm. Our analysis use ratio-based scheme and hybrid scheme to renormalize the equal-time bilocal quark-bilinear matrix elements. We extract first few moments and reconstruct the x-dependent PDF using NNLO leading-twist...
We compute hybrid static potentials in SU(3) Yang-Mills theory at short quark-antiquark separations using four different small lattice spacings as small as 0.04 fm. The resulting static potentials are important e.g. when computing masses of heavy hybrid mesons in the Born-Oppenheimer approximation. We also discuss and exclude possible systematic errors from topological freezing, the finite...
We report an implementation of a multigrid solver on supercomputer Fugaku, which uses A64FX cpu with Arm architecture. On Fugaku, a highly optimized BiCGStab solver with domain decomposed preconditionor for Clover fermion, called QCD Wide Simd library (QWS), is available. Multigrid solvers are made from several components so that one can use a part of QWS such as Clover kernel. As the original...
In the holographic approach to cosmology, cosmological observables are described in terms of correlators of a three-dimensional boundary quantum field theory. As a concrete model, we study the 3D massless SU(N) scalar matrix field theory with a $\phi^4$ interaction. On the lattice, the energy-momentum tensor (EMT) in this theory can mix with the operator $\phi^2$. We utilise the Wilson Flow to...
We show that using the multi-splitting algorithm as a preconditioner for the domain wall Dirac linear operator, arising in lattice QCD, effectively reduces the inter-node communication cost, at the expense of performing more on-node floating point and memory operations. Correctly including the boundary \textit{snake} terms, the preconditioner is implemented in the QUDA framework, where it is...
The transversity parton distribution function probes the x-dependent difference between quarks with their spins aligned and anti-aligned with the transverse polarization of the nucleon. The chiral-odd nature of the transversity makes it experimentally harder to extract than unpolarized distributions, thereby making the lattice determination crucial. In this talk, we will present results on...
Flux tube spectra are expected to have full towers of levels due to the quantization of the string vibrations. We study a spectrum of flux tubes with static quark and antiquark sources with pure gauge SU(3) lattice QCD in 3+1 dimensions up to a significant number of excitations. To go high in the spectrum, we specialize in the most symmetric case $\Sigma_g^+$, use a large set of operators,...
We present Lyncs, a Python API for Lattice QCD currently under development. Lyncs aims to bring several widely used libraries for Lattice QCD under a common framework. Lyncs flexibly links to libraries for CPUs and GPUs in a way that can accommodate additional computing architectures as these arise, ensuring performance-portability for the calculations while maintaining the same high-level...
We study a recently proposed formulation of U(1) lattice field theory with electric and magnetic matter based on the Villain formulation. This discretization allows for a duality that gives rise to relations between weak and strong coupling. We use a worldline version of the model to overcome the complex action problem and discuss suitable algorithms for its simulation. We investigate the...
The era of exascale computing enables the generation of ever-finer gauge configurations, capturing gauge-fermion physics with unprecedented accuracy. This approach to the continuum comes with a super-linear increase in the cost of the iterative Krylov solve of the Dirac fermion operator, the phenomena of critical slowing down. Multi-grid methods are the optimal approach to addressing this...
We show how to compute electromagnetic polarizabilities of charged hadrons on the lattice without using background fields. The low-energy behavior of the Compton scattering amplitude is matched to matrix elements of current-current four point functions. Working in momentum space, formulas for electric polarizability and magnetic polarizability are derived for both charged pion and proton....
Researchers working in lattice field theory built an established
community since the early 1990s, around the same time when
the arXiv was created. The fact that this field has a specific
arXiv section provides a unique opportunity for a statistical
study of its evolution over the last three decades.
We present data for the annual number of papers and citations,
in total and separated by...
The $O(3)$ non-linear sigma model (NLSM) is a prototypical field theory for QCD and ferromagnetism, featuring topological qualities. Though the topological susceptibility $\chi_t$ should vanish in physical theories, lattice simulations of the NLSM find that $\chi_t$ diverges in the continuum limit. We study the effect of the gradient flow on this quantity using a Markov chain Monte Carlo...
Application of Hybrid Monte Carlo technique allowed us to perform the simulations of electronic properties of suspended graphene at large enough lattices to directly observe the infrared renormalization of the Fermi Velocity for the first time in non-perturbative Quantum Monte Carlo calculations. We compared the results with experiment, and demonstrated the agreement in the specific case, when...
In 2020 we deployed QPACE 4, which features 64 Fujitsu A64FX model FX700 CPUs interconnected by InfiniBand EDR. QPACE 4 runs an open-source software stack. For LQCD simulations we ported the Grid LQCD framework to support the Arm Scalable Vector Extension (SVE). In this contribution we discuss our SVE port of Grid, the status of SVE compilers and the performance of Grid. We also present...
We discuss the status, portability and performance of the Grid package for lattice QCD. Accelerated computing nodes are increasingly common and increasingly varied. Programming for all of them is a considerable pain that gets in the way of science. A major update to Grid abstracts the differences and will run well with single source code on SIMD CPUs and on CUDA, HIP and SyCL suitable for...
We report on a two-flavor lattice QCD determination of the $B_s \to D_s$
and $B_s \to D^*_s$ transitions, which in the heavy quark limit can be
parameterized by the form factors ${\cal G}$, and $h_{A_1}$, $h_{A_2}$ and
$h_{A_3}$. In the search of New Physics through tests of lepton-flavour
universality, $B_s$ decay channels are complementary to $B$ decays and
widely studied at $B$...
OpenMP has been the programming model of choice for shared-memory parallelism on multi-/many-core CPUs for a long time. Recent additions to the OpenMP standard have also enabled the support for offloading certain computations to compute accelerators such as GPUs. This potentially allows us to have a single code written with OpenMP directives that can be executed on both CPU and CPU+GPU...
We will present our recent efforts on using tensor cores, which are available on NVIDIA GPUs starting from the Volta architecture, to speed up the math intensive kernels in QUDA. A light-weighted abstraction of the CUDA PTX matrix multiply-add (MMA) instruction is added in order to efficiently stage data through the different layers of GPU memory. Specifically the efforts include:
- Use...
We study the high temperature transition in pure $SU(3)$ gauge theory and in full QCD with 3D-convolutional neural networks trained as parts of either unsupervised or semi-supervised learning problems. Pure gauge configurations are obtained with the MILC public code and full QCD are from simulations of $N_f = 2+1+1$ Wilson fermions at maximal twist. We discuss the capability of different...
The tensor renormalization group is a promising numerical method used to study lattice statistical field theories. However, this approach has been prohibitively expensive in 2+1 and 3+1 dimensions until recently. Here we use relatively new tensor renormalization group methods to study an effective three-dimensional $Z_3$ model for the heavy-quark, high-temperature, strong-coupling limit of...
We construct a tensor network representation of the partition function
for the massless Schwinger model on a two dimensional lattice using staggered fermions. The tensor network representation
allows us to include a topological term. Using a particular
implementation of the tensor renormalization group (HOTRG) we calculate the phase diagram of the
theory. For a range of values of the...
Recent improvements in the numerical lattice simulation have been achieved by making use of the eigenvalue spectrum of the lattice Dirac operator or its variants. The Lanczos algorithm has been employed for that purpose, and the lattice community has studied its improvements with different approaches. We investigate state-of-the-art Lanczos eigensolvers available in the Grid and the QUDA...
We present a calculation of the pion and kaon form factors and generalized form factors using matrix elements of local operators. We use an ensemble of two degenerate light, a strange and a charm quark (Nf=2+1+1) of maximally twisted mass fermions with clover improvement. The quark masses are chosen so that they reproduce a pion mass of about 260 MeV, and a kaon mass of 530 MeV. The lattice...
"Calculating the x-dependence of PDFs and GPDs from lattice QCD has become feasible in the last years due to novel approaches. In this work, we employ the quasi-distributions method, which relies on matrix elements of non-local operators, matched to the light-cone distributions using Large Momentum Effective Theory (LaMET). In this presentation, we focus on results for the first-ever lattice...
As part of our study of two-point functions in SU(3) lattice gauge theory, we have carried out a comparative analysis of Landau Gauge Fixing algorithms, which complements similar existing studies for the SU(2) case. We present the results of our optimization analysis for the Landau Gauge Fixing overrelaxation and stochastic overrelaxation algorithms. By studying the distribution of necessary...
Lattice tensor representations are used to investigate the lattice Landau gauge gluon propagator for the 4-dimensional, pure SU(3) Yang-Mills gauge theory.
Due to the different symmetry structure of hypercubic lattices compared to the continuum space-time, lattice correlation functions are described by different tensor structures. Therefore, form factors describing lattice correlation...
We report progress in preconditioning Wilson-type Dirac operators in 1+1 dimensional U(1) lattice field theory using a neural network. We have developed a convolutional network that produces a preconditioner of comparable sparsity to the input operator. Once the model is trained, applying it to produce preconditioners is computationally cheap; with an optimized implementation, the neural...
We present recent results on the QCD equation of state (EoS) with 2+1+1 flavors of highly improved staggered quarks (HISQ). The EoS is calculated with high statistics on lattices with temporal extent $N_\tau=6$ and $8$. The available temperature range extends up to about 960 MeV. The strange and charm quark masses are tuned to the physical values while the light quark mass corresponds to the...
We study the spectrum of the bottomonium system at non-zero temperature using the NRQCD approximation. A maximum likelihood method is used with a Gaussian ansatz for the ground state spectral contribution rather than the traditional delta function. This gives access to the state’s width. We apply this approach to the FASTSUM’s anisotropic ensembles and compare results for the ground state...
We propose using Normalizing Flows as a trainable kernel within the molecular dynamics update of Hamiltonian Monte Carlo (HMC). By learning (invertible) transformations that simplify our dynamics, we can outperform traditional methods at generating independent configurations. We show that, using a carefully constructed network architecture, our approach can be easily scaled to large lattice...
Using simulations in QCD+QED we investigate electromagnetic corrections to charged pion decay. We calculate pion-muon three-point functions, and analyze the dependence on time and momentum transfer to investigate the interplay between the strong, weak and electromagnetic effects.
General-purpose Markov Chain Monte Carlo sampling algorithms suffer from a dramatic reduction in efficiency as the system being studied is driven towards a critical point through, for example, taking the continuum limit. Recently, a series of seminal studies suggested that normalizing flows - a class of deep generative models - can form the basis of a sampling strategy that does not suffer...
Lattice Field Theory correlation functions are usually difficult to model in momentum space. As a result, fitting to a sum of poles in frequency space can be preferable especially when the signal contains an additive constant as this constant is isolated in the zero-frequency mode. To help model the spectroscopy in frequency space, we implemented a black-box method that we call rational...
There are several examples of light flavor-singlet scalar mesons in near-conformal gauge theories, including SU(3) $N_f=8$ gauge theory. We present a finite volume study of the scalar mass and scalar decay constant.
QED in the presence of strong external fields is relevant to Laser physics, Accelerator physics, Astrophysics and Condensed Matter physics. Standard methods of relativistic quantum mechanics and QED, including perturbation theory, have their limitations. To go beyond this, approximate non-perturbative methods such as the Schwinger-Dyson approach have been applied. We are simulating Lattice QED...
A high-statistics computation of meson-baryon scattering amplitudes is presented on a single ensemble from the Coordinated Lattice Simulations (CLS) consortium with $m_{\pi}=200{\rm MeV}$ and $N_{\rm f} = 2+1$ dynamical fermions. The finite-volume approach is employed to determine the lowest few partial waves from ground and excited state energies computed by solving the Generalized Eigenvalue...
Lattice QCD at nonzero baryon density is a big challenge in hadron physics. In this talk, I discuss the quantum computation of lattice gauge theory at nonzero density. I present some results of a benchmark test based on the quantum variational algorithm.
We present a calculation of the connected-diagram contributions to the
first three non-trivial Mellin moments for the pion and kaon extracted
directly in lattice QCD using local operators with up to 3 covariant
derivatives. We reconstruct the $x$-dependence of the pion and kaon
PDFs via fits to our results. We find that the reconstruction is
feasible and that our lattice data favor a...
The gradient flow, which exponentially suppresses ultraviolet field fluctuations and removes ultraviolet divergences (up to a multiplicative fermionic wavefunction renormalization), can be used to describe real-space Wilsonian renormalization group transformations and determine the corresponding beta function. We propose a new nonperturbative renormalization scheme for local operators that...
We discuss the flavor number dependence of QCD at finite density by using the complex Langevin method. In our previous works, the complex Langevin method is confirmed to satisfy the criterion for correct convergence in some regions, such as $\mu / T = 5.2-7.2$ on $8^3 \times 16$ and $\mu / T = 1.6-9.6$ on $16^3 \times 32$ using $N_f = 4$ staggered quarks at $\beta = 5.7$. We extend this study...
We use the Infinite Volume Reconstruction Method to calculate the charged/neutral pion mass difference. The hadronic tensor is calculated on lattice QCD and then combined with an analytic photon propagator, and the mass shift is calculated with exponentially-suppressed finite volume errors. In this talk we discuss the Feynman diagrams relevant to the pion mass difference and we recapitulate...
Finding ground states and low-lying excitations of Hamiltonians is one of the most important problems that can be solved with near-term quantum computers. It can be utilized in fields ranging from optimization over chemistry and material science to particle physics. In this work, we propose an efficient error mitigation scheme that is independent of the Hamiltonian and the concrete noise...
The hadronic physics of the simplest semileptonic decays of $\Lambda_b$'s and $\Lambda_c$'s, in which both the initial and final baryons have $J^P=\frac12^+$, is by now quite well understood. We have begun exploring more complicated processes with $J^P=\frac12^-$ and $J^P=\frac32^-$ baryons in the final state, which have a rich phenomenology but are more challenging for theory and experiment....
Hyperon physics is expected to play a role in neutron stars, where the extreme neutron degeneracy pressure could push neutrons into hyperons; indeed, the composition of neutron stars contributes to the "softness" or "stiffness" of the equation of state, therefore setting limits on the possible sizes and masses of neutron stars. In this talk, I will present calculations of hyperonic...
We will present how to calculate propagators on Chroma+QUDA with overlap, HISQ (highly improved staggered quark) and twisted-mass fermion actions. Those actions are not fully supported before and now most of the actions can be used in Chroma framework efficiently. The multi-grid speed-up for the HISQ and Twisted mass actions using QUDA will also be presented.
When using deep inelastic scattering (DIS) to probe hadronic structure, we can use the operator product expansion to approximate the product of currents, using the operators' twist to suppress higher order effects. On the lattice, these operators experience power divergent mixing, which we aim to control by introducing the gradient flow. We study an example in perturbation theory.
Large-momentum effective theory provides a way to extract the parton physics from lattice data based on first-principle calculation. In applying large-momentum effective theory, renormalization of
the Euclidean correlators in lattice regularization is a challenge due to
linear divergences in the self-energy of Wilson lines.
Based on lattice QCD matrix elements of the quasi-PDF operator at...
We apply the complex Langevin method (CLM) to overcome the sign problem in 4D SU(2) gauge theory with a theta term extending our previous work on the 2D U(1) case. The topology freezing problem can be solved by using open boundary conditions in all spatial directions, and the criterion for justifying the CLM is satisfied even for large $\theta$ as far as the lattice spacing is sufficiently...
I discuss symmetric mass generation (SMG) and its relevance to the problem of constructing lattice chiral fermions. A necessary condition for SMG is the
cancellation of certain discrete anomalies which constrain the number of
fermions to multiples of sixteen. I give some examples of models based on
reduced staggered fermions that are capable of SMG.
At low temperature and high density, quark matter is expected to be a color superconductor(CSC). In a recent study based on lattice perturbation theory, we have found that the CSC occurs even on a lattice with a small spatial length. According to our previous study (JHEP10(2020)144), the complex Langevin method is expected to work on such a lattice without suffering from the excursion and...
Recent lattice QCD results for the first two low-lying odd-parity excitations of the nucleon have revealed that they have magnetic moments consistent with constituent-quark-model expectations. Thus, in constructing a basis of states to describe scattering in this channel, one should not represent both odd-parity excitations by a single three-quark basis state. Two single-particle basis...
Hadron spectral functions are important quantities as they carry all the information of hadrons. Unfortunately they cannot be computed directly on the lattice, and can only be extracted from Euclidean two-point temporal correlation functions which are directly computable in lattice QCD. The extraction of spectral functions from correlation functions is an inverse problem, and the most commonly...
We compute the inclusive neutrino-nucleon scattering cross sections from
the first principles of QCD. This is highly relevant to the recent and
future $\nu-N$ scattering experiments , whose energy regime is excessively low
for the perturbative analysis to hold. We use a technique recently
proposed
to treat the inclusive contributions on the lattice. We compute the
forward...
Renormalization constants of the scalar and tensor currents are calculated for overlap fermions on domain-wall fermion configurations. We perform zero, one or two steps of hypercubic smearing in constructing the overlap Dirac operator and examine the discretization effects in the renormalization constants of quark bilinears and check the dependence of those effects on the level of smearing....
We construct a four dimensional lattice gauge theory in which fermions acquire mass without
breaking symmetries as a result of gauge interactions. We start from
a $SU(2)$ lattice Yang-Mills theory with staggered fermions transforming under an additional
global $SU(2)$ symmetry. The fermion representations are chosen
so that single site bilinear mass terms vanish identically. A symmetric...
A universal supervised neural network (NN) relevant to study phase transitions
is constructed. The validity of the built NN is examined by applying it to
calculate the criticalities of several three-dimensional (3D) and two-dimensional (2D) models including the 3D classical $O(3)$ model, the 3D 5-state ferromagnetic Potts model, a 3D dimerized quantum antiferromagnetic Heisenberg model as...
We construct a method for computing the spectral sum appearing in the Shifman-Vainshtein-Zakharov (SVZ) QCD sum rule. The method gives results consistent with the operator product expansion (OPE) of the $s\bar{s}$ correlation function in the vector channel. The application of this method to other channels is useful for operator renormalization as well as the test of perturbative QCD and OPE.
In Phys.Rev.Lett.107,091601, T.Kawanai and S.Sasaki extended HAL QCD method to the ccbar system and showed numerically that the qqbar potential obtained from the Nambu-Bethe-Salpeter wave function agrees with the qqbar potential obtained from Wilson loop in the heavy quark mass limit. However, it is not known how these two potentials can agree. In this talk, the relation between these two...
We study a strongly interacting lattice field theory model with two massless flavors of staggered fermions in three space-time dimensions. We consider the phase diagram of the model as a function of two couplings: (1) a lattice current-current interaction $U$, and (2) an on-site four-fermion interaction $U^\prime$. While individually both these interactions drive second order phase transitions...
We present a novel method to evaluate the real-time path integral for 1+1 dimensional real scalar phi^4 theory. The method can be combined with tensor network coarse-graining schemes. As a demonstration we will show numerical results of two-point correlator in a small lattice.
We present preliminary results for a lattice study of the chiral and continuum limit of pseudoscalar mass and decay constant for $SU(N_c)$ gauge theory with $N_c=3,4,5$ colors and $N_f=2$ degenerate fermions. Clover fermions are used. We fit these observables to predictions of Wilson chiral perturbation theory. Model-averaging is used to determine an appropriate range of quark masses for the...
The interpretation of gradient flow as a Wilsonian renormalization group (RG) transformation allows one to determine the continuous RG beta function. This approach is alternative to the finite-volume step-scaling function. Unlike step-scaling methods, where the lattice volume must provide the only scale, the continuous beta function can be used even in the confining regime. We demonstrate this...
The nucleon forward Compton amplitude describes the process of a virtual photon scattering on a nucleon. It is an important object which encodes insights into hadronic structure. The real part of this amplitude contains a component that is unconstrained by a dispersive representation in terms of inelastic scattering data. This component, commonly referred to as the `subtraction function',...
We apply the persistent homology analysis to effective models of quantum chromodynamics (QCD) with heavy quarks on a rectangular lattice to investigate the confinement-deconfinement transition. In this talk, I will concentrate on the effective Polyakov-line model and the Potts model with external field as the QCD effective model. The configurations are mapped onto the complex Polyakov-line...
Gauge anomaly in 4-dimensions can be viewed as a current inflow into an extra-dimension, where the total phase of the fermion partition function is given in a gauge invariant way by the Atiyah-Patodi-Singer(APS) eta-invariant of a 5-dimensional Dirac operator. However, this formalism requires a non-local boundary condition, which makes the physical roles of edge/bulk modes unclear and the...
Abstract: we study the confinement-deconfinement transition and $Z_2$ symmetry in lattice $Z_2+$Higgs theory in $3+1$ dimensional Euclidean space using lattice Monte Carlo simulation methods. In pure $Z_2$ gauge theory the CD transition is first order. Polyakov loop acquires non-zero thermal average value in the deconfined phase and the $Z_2$ symmetry is spontaneously broken. The $Z_2$...
This work seeks to enable more detailed numerical probes into nuclear structure using the standard model through lattice QCD. The computational cost required to compute nuclear correlations functions grows exponentially in the number of quarks, leaving the study of many large nuclear bound states inaccessible. However, these tensor expressions exhibit a high degree of permutation symmetry that...
The precise equivalence between discretized Euclidean field theories and a certain class of probabilistic graphical models, namely the mathematical framework of Markov random fields, opens up the opportunity to investigate machine learning from the perspective of quantum field theory. In this talk we will demonstrate, through the Hammersley-Clifford theorem, that the $\phi^{4}$ scalar field...
Motivated by the early-time dynamics of the quark-gluon plasma in high-energy heavy-ion collisions, we extract gluonic spectral functions of overoccupied gauge theories far from equilibrium using classical-statistical lattice simulations. In 3+1 dimensions we find that the spectral function exhibits quasiparticle excitations at all momenta that are mostly consistent with perturbative...
We investigate the role of inhomogeneous field configurations in systems with a spontaneously broken continuous global symmetry. Textbooks tell us that the quantum effective potential of the system is flat in the thermodynamic limit. At the same time, spontaneous breaking is defined through the double limit, infinite volume at finite explicit breaking sources, which then approach zero. This...
With increasing interest in machine learning techniques for lattice gauge theory, it becomes important to develop suitable neural network architectures that are compatible with the fundamental symmetries that lie at the heart of lattice QCD. We propose a novel neural network architecture called lattice gauge equivariant convolutional neural networks (L-CNNs) [1] that can be applied to problems...
We present an overview of the RQCD and ALPHA collaboration's combined effort on charm decay constants. Our calcluations are based on the $N_\mathrm{f}=2+1$ CLS ensembles including the physical point. We discuss our analysis strategy and present results for the pseudoscalar and vector decay constants $f_{D_{(\mathrm{s})}}$ and $f_{D_{(\mathrm{s})}^\ast}$ as well as the coupling of the...
Lattice QCD is a first principle tool that allows to solve the theory in the non-perturbative regime. The Landau gauge quark, gluon and ghost propagator have been recently computed using both large physical volumes to access the IR region and large gauge ensembles that reduce the corresponding statistical uncertainties. However, lattice QCD only offers a table of numbers and further treatment...
The study of jets in heavy ion collisions provides important information about the interaction of partons with the medium that they traverse. The seeds of jets are highly energetic partons, which are produced from hard scatterings during the collision event. As such, they are affected by all different stages of the medium's time evolution, including the glasma, which is the pre-equilibrium...
The lattice three-gluon vertex in the Landau gauge is revisited using a large physical volume $\sim(8\, \text{fm})^4$ and a large statistical ensemble. The improved calculation explores the symmetries of the hypercubic lattice to reduce the statistical uncertainties and to address the evaluation of the lattice artefacts. In particular we focus on the low energy behaviour of the vertex and...
In recent years, the use of machine learning has become increasingly popular in the context of lattice field theories. An essential element of such theories is represented by symmetries, whose inclusion in the neural network properties can lead to high reward in terms of performance and generalizability. A fundamental symmetry that usually characterizes physical systems on a lattice with...
We will present a lattice QCD computation of the decay constants for the pseudoscalar mesons K and D(s) in the isosymmetric limit by the Extended Twisted Mass Collaboration (ETMC). Simulations of Nf=2+1+1 dynamical quarks have been performed with the twisted mass fermion action at three values of the lattice spacing, where the masses of the light, strange and charm quarks are all tuned at...
We report on our ongoing determination of the charm quark mass and the masses and decay constants of various charmed mesons, obtained within a mixed-action setup. We employ $N_f=2+1$ CLS ensembles combined with a Wilson twisted mass valence action that eliminates the leading $O(a)$ effects from our target observables. Alongside our preliminary results, we will discuss an exploration of GEVP...
The Polyakov loop expectation value $\langle P\rangle$ is an order parameter of the deconfinement transition in the heavy quark mass regime, whereas its sensitivity to the deconfinement of light, dynamical quarks is not apparent. From the perspective of an effective Lagrangian in the vicinity of the chiral transition, the Polyakov loop, $P$, is an energy-like observable, and $\langle P\rangle$...
We interpret machine learning functions as physical observables, opening up the possibility to apply "standard" statistical-mechanics methods to outputs from neural networks. This includes histogram reweighting and finite-size scaling, to analyse phase transitions quantitatively, as well as the incorporation of predictive functions as conjugate variables coupled to an external field within the...
We study the Landau-gauge quark-gluon vertex with 2 flavours of O(a) improved Wilson
fermions, for several lattice spacings and quark masses. In the limit of vanishing gluon momentum, we find that all nonzero form factors have a significant infrared strength, and that the leading form factor $\lambda_1$, multiplying the tree-level vertex structure, is significantly enhanced in the infrared...
We will present the pion mass and decay constant using the overlap fermion valence on DW fermion sea at several lattice lattice spacings. The mixed action effect in the lattice calculation is also studied, and the result suggests that the mixed action effect with overlap valence on DW sea would be proportional to the fourth power of the lattice spacing. The preliminary determination of the...
Semileptonic $D \to{}K \ell \nu$ decays provide one angle of attack to get at the CKM matrix element $V_{cs}$, complementary to the study of leptonic $D_s$ decays. Here HPQCD present the results of an improved determination of $V_{cs}$, recently released on the arXiv (2104.09883).
We discuss a new, precise determination of $D\to K$ scalar and vector form factors from a lattice calculation...
We study analytic structures of the gluon, quark, and ghost propagators in the Landau-gauge QCD and general properties from the existence of unusual singularities. First, we investigate analytic structures of the QCD propagators using the massive Yang-Mills model, in which the one-loop gluon and ghost propagators are in good agreement with the numerical lattice results in the Landau gauge. We...
We study the scaling behavior of the (2+1)-QCD crossover region towards the chiral limit with smaller-than-physical light quark mass gauge ensembles, generated using the HISQ fermion discretisation. We calculate the leading curvature coefficient of the QCD crossover line at smaller light quark masses and compare it with the curvature in the chiral limit obtained using scaling arguments. At...
In this talk, I will discuss how thermodynamic observables of lattice field theories can be estimated using machine learning. Specifically¸ deep generative models are used to estimate the absolute value of the free energy. This is in contrast to MCMC-based methods which are limited to estimating differences of free energies. These methods come with the same asymptotic guarantees as the...
We present the results of HPQCD's recent calculation of the $B_c \to J/\psi$ semileptonic form factors and $R(J/\psi)$ for the first time from lattice QCD using the heavy-HISQ method. We also present results from lattice QCD, using the heavy-HISQ method, for the $B_s \to D_s^*$ semileptonic form factors and $R(D_s^*)$. We give a value for $|V_{cb}|$ computed using our results for the full...
Machine learning is becoming an established area of research in lattice field theories, with prominent applications to phase classification, configuration generation, and noise reduction. When moving beyond the toy models, scalable methods to learn phases of matter are needed. In this talk, we compare two possible avenues to speed up the methods for classifying phase transitions in the 2D...
At finite imaginary values of the chemical potential, QCD is free of the sign
problem. Moreover, at high temperatures the partition function exhibits
a new symmetry (the Roberge-Weiss symmetry) connecting phases
with different orientations of the Polyakov loop, and the corresponding
phase transitions between these.
In this contribution we investigate the perturbative one-loop
effective...
We report on the status of the analysis of the static potential in 2+1+1-flavor QCD. The static potential is obtained by measuring Wilson loops using the HISQ action, yielding the scales $r_{1}/a$, $r_{2}/a$, and the string tension $\sigma$. We put our emphasis on the possible effects due to the dynamic charm quark by comparing the lattice results to continuum results of the static potential...
A recently proposed approach to inclusive semi-leptonic decay rate on the lattice allows for the calculation of various quantities (differential distributions and moments) in different subchannels. We systematically compare the lattice QCD results for unphysically light bottom and strange quarks with OPE-based predictions, including leading order perturbative and O(1/m^3) power corrections,...
In this talk I will present lattice results regarding the glueball
spectrum, the localization of Dirac eigenmodes and thermal monopoles
properties in trace-deformed YM theory. Trace deformation is an extra
piece added to the usual YM action, which stabilizes center symmetry
also in the limit of small compactification length. The study of
trace-deformation could give a deep insight on the...
We determine, with Twisted Mass Lattice QCD simulations and adopting the RM123 method, the charged/neutral pion mass difference $M_{\pi_{+}} - M_{\pi_{0}}$ at order $\mathcal{O}(\alpha_{em})$ in the QED interactions and present preliminary results for $M_{\pi_{+}} - M_{\pi_{0}}$ at order $\mathcal{O}\left( (m_{d}-m_{u})^{2}\right)$ in the strong isospin-breaking term. The latter contribution...
We present recent results [1] in which we apply unconditionally stable stochastic partial differential equations solvers [2] to complex Langevin in real-time [3]. This allows us to avoid runaway solutions in principle and enables simulations at relatively large Langevin step size. We show that implicit schemes act as a regulator of the underlying path integral and give a heuristic estimate of...
QCD with heavy dynamical quarks exhibits a first order thermal transition which is driven by the spontaneous breaking of the global $Z_3$ center symmetry. Decreasing the quark masses weakens the transition until the corresponding latent heat vanishes at the critical mass.
We explore the heavy mass region with three flavors of staggered quarks. We analyze the Polyakov loop and its moments in a...
Effective 3d Polyakov loop theories derived from QCD by strong coupling and hopping expansions are valid for heavy quarks and can also be applied to finite chemical potential, due to their considerably milder sign problem. We apply the Monte-Carlo method to the $N_f=1,2$ effective theories up to $\mathcal{O}(\kappa^4)$ in the hopping parameter at zero $\mu$ to determine the critical quark...
We present HPQCD’s results of the first lattice QCD calculation of the weak matrix elements for $B_c^+ \to D^0 \ell^+ \nu_{\ell}$ facilitated by a $b \to u$ transition. Together with observation of this process from LHCb, our form factors will lead to a new determination of $V_{ub}$. In tandem, we also calculate the form factors for rare $B_c^+ \to D_s^+ \ell^+ \ell^-$. Results are derived...
The numerical sign problem is one of the major obstacles to the first-principles calculations for important physical systems, such as finite-density QCD, strongly-correlated electron systems and frustrated spin systems, as well as for the real-time dynamics of quantum systems. The tempered Lefschetz thimble method (TLTM) [1] was proposed as a versatile algorithm towards solving the numerical...
We compare the behavior of the analytic instanton-dyon solutions to zero and near-zero-modes of the overlap Dirac operator measured on the finite temperature 2+1 flavor lattice QCD configurations, generated with domain wall fermion discreitzation. By performing numerical fit to the (near) zero-modes from lattice calculations, we extract information about the typical distance between the dyons...
In this talk we present preliminary results for the masses of the proton, neutron and Omega- baryons obtained from $n_f$=1+2+1 QCD+QED lattice simulations performed using C$^*$ boundary conditions. Spin-1/2 and spin-3/2 baryon two-point correlators are extracted from full QCD+QED lattice simulations through an extension to the OpenQ$^*$D publicly available code. The correlators are computed by...
Establishing whether or not the famous first order corner at small quark masses exists in the Columbia plot is one of the major open issues in studies of the phase diagram of QCD. We delve into this problem and present results from our ongoing study of the chiral limit in three-flavor QCD using the Highly Improved Staggered Quark (HISQ/tree) action.
We investigate four quark masses, which...
We numerically study the Hamiltonian lattice formulation of the Schwinger model with two fermion flavors using matrix product states. Keeping the mass of the first flavor at a fixed positive value, we tune the mass of the second flavor through a range of negative values, thus exploring a regime where conventional Monte Carlo methods suffer from the sign problem. Our results show signatures of...
The Schwinger model is often used as a testbed for conceptual and numerical
approaches in lattice field theory. Nevertheless, some of the rich physical
properties of the model in anisotropic volumes have not yet been tested.
For the multi-flavor finite temperature Schwinger model there is an
approximate solution by Hosotani et al. based on bosonization. We perform
thorough comparisons...
We investigate the renormalization of the Gluino-Glue operator, using both Lattice Perturbation Theory (LPT) and a Gauge Invariant Renormalization Scheme (GIRS). The latter scheme involves gauge-invariant Green's functions of two operators at different space-time points, which can be also computed via numerical simulations. There is no need to fix a gauge and the mixing with gauge noninvariant...
Partially twisted boundary conditions are widely used for improving the momentum resolution in lattice computations of hadronic correlation functions. The method is however expensive since every additional twist requires computing additional propagators. We propose a novel variance reduction technique that exploits statistical correlations between correlators at different twists to reduce the...
Topological terms contribute an imaginary part to the action such that for a numerical simulation of such systems the corresponding complex action problem has to be overcome. We address this task with newly developed density of states techniques combined with open boundary conditions that lift the integer quantization of the topological charge. We present results for U(1) and SU(2) lattice...
$\mathcal{N} = 1$ supersymmetric Yang-Mills theory describes gluons interacting with gluinos, which are spin 1/2 Majorana particles in the adjoint representation of the gauge group. In addition to glueballs and mesonic bound states, the theory contains colour neutral bound states of three gluinos, which are analogous to baryons in QCD. We calculate their correlation functions, involving...
We present work designed to compute baryon masses on $N_f=2+1$ CLS ensembles including isospin breaking effects due to non-degenerate light quark masses and electromagnetic interactions. These effects are determined at leading order via a perturbative expansion around the iso-symmetric theory. We furthermore apply a group theoretical operator construction for the various interpolators...
The Columbia plot specifies the order of the $N_f=2+1$ QCD thermal transition as a function of the quark masses. Since massless quarks cannot be simulated directly, the nature of the phase transition in the limit of vanishing $u,d$-quark masses has remained elusive, with different discretisations showing different orders of the transition in the small mass regime. We propose a modified...
Experiments show that the flavor-singlet pseudoscalars usually have large production ratios in the radiative decays of $J/\psi$.
In this work we perform the first lattice investigation on this topic based on a gauge ensemble generated on an anisotropic lattice with two degenerate light dynamical quarks. The mass parameter of the light quarks is tuned to give a pion mass around 300 MeV. The...
We numerically study QCD with a single quark flavour on the lattice probing predictions from effective field theories that are equivalent to minimal super-symmetric Yang-Mills theory in the large $N_c$ limit.
The hadronic spectrum including excited states is analyzed using one gauge coupling and several physical volumes and fermion masses. We use the LapH method and also compute...
We reconstruct spectral functions from ghost and gluon propagators obtained through lattice QCD calculations with dynamical quarks. To this end, we employ Gaussian process regression (GPR) using kernel parametrizations that explicitly encode the analytically derived asymptotic scaling properties in the infrared and ultraviolet. The proposed ansatz allows us to consistently improve the...
We demonstrate that classical bit-flip correction can be employed to mitigate measurement errors on quantum computers. Importantly, our method can be applied to any operator, any number of qubits, and any realistic bit-flip probability. Starting with the example of the longitudinal Ising model, we then generalize to arbitrary operators and test our method both numerically and experimentally on...
In a previous work the regulator dependence of inhomogeneous phases in the $2+1$-dimensional Gross-Neveu model has been studied within the mean-field approximation. These are phases, where in addition to chiral symmetry also translational symmetry is broken. Inhomogeneous condensates are a feature shared among various strong-interaction models and not unique to the $2+1$-dimensional...
Readout errors are among the most dominant sources of error on current noisy intermediate-scale quantum devices. Recently an efficient, scaleable method for mitigating such errors has been developed. Here, we benchmark this correction protocol on IBM's and Rigetti's quantum devices. Measuring observables in the computational basis, we demonstrate how the mitigation procedure improves the...
Monopoles play crucial roles in the color confinement mechanism through condensing in the QCD vacuum, and the instantons induce spontaneous chiral symmetry breaking. Monopoles and instantons are closely related to each other and interact among quarks and gluons in the QCD vacuum. It is very interesting if we can show a clue to observe monopoles and instantons by experiments. Therefore, we...
Gauge theories with fermions in adjoint and fundamental representations are relevant for many different applications including composite Higgs models and general aspects of the confinement problem. In this talk, I will present first results from simulations of SU(2) gauge theory with two Dirac fermions in the fundamental representation and one adjoint Majorana flavour. In this context, I will...
We investigate the parity odd $\Delta I = 1$ pion-nucleon coupling $h^1_\pi$ from lattice QCD. With the PCAC-based use of a parity-conserving effective Hamiltonian, we extract the coupling by determining the nucleon mass splitting arising from effective 4-quark interactions using the Feynman-Hellmann theorem. We present preliminary results of the mass shift for a $32^3 \times 64$ ensemble...
The US electron ion collider (EIC) was established firmly as a project in the Office Of Science in January 2020. The EIC will be built at Brookhaven National Laboratory (BNL) jointly by BNL and Jefferson Lab working as partners. An EIC Project has been setup and is making progress fast. The EIC Users Group is evolving in to proto-collaborations which are expecting to submit preliminary...
Panelist Biographies:
Professor Aida El-Khadra received her PhD. in 1989 from the University of California, Los Angeles, after receiving her diploma from Freie Universitaet, Berlin, Germany. She held postdoctoral research appointments at Brookhaven National Laboratory, Fermi National Accelerator Laboratory, and the Ohio State Univerity before joining the Illinois faculty in 1995. El-Khadra...
We introduce a on-parameter family of SU(N) gauge actions which, when used in combination with an HMC update algorithm, prevent the gauge system from entering an artificial bulk-"phase". We briefly discuss the (presumed) mechanism behind the bulk-prevention and present test results for different SU(N) gauge groups.
In modern lattice simulations, conventional update algorithms do not allow for tunneling between topological sectors at fine lattice spacings. We compare the viability of multiple (less commonly used) algorithms with respect to proper sampling of all topological sectors in the Schwinger model. We briefly comment on the prospects of applying these methods to 4-dimensional SU(3) simulations.
The origin of the proton spin has attracted a lot of attention since the first surprising result from the European Muon Collaboration about 30 years ago. We present a significant step towards solving the proton spin puzzle. The calculation is done using $N_f=2+1+1$ twisted mass fermions directly at the physical point. Both gluon and quark contributions to the proton spin are evaluated, where...
We consider three-flavor QCD and perform a determination of the low energy coupling $\hat g$ of SU(2) Heavy Meson Chiral Perturbation Theory. It is the $B^*B\pi$ coupling in the limit of static heavy and chiral light quarks in $N_\mathrm{f}=2+1$ flavor QCD and has not been determined with precision thus far. The calculation is performed on the $2+1$ flavor CLS ensembles using the summed GEVP...
The last years have seen significant developments in methods relating two- and three-particle finite-volume energies to scattering observables. These relations holds for both weakly and strongly interacting systems, and studying their predictions in limiting cases can provide important cross checks as well as giving useful insights to the general formulae. In this talk, I present analytic...
Standard sampling algorithms for lattice QCD suffer from topology freezing (or critical slowing down) when approaching the continuum limit, thus leading to poor sampling of the distinct topological sectors. I will present a modified Hamiltonian Monte Carlo (HMC) algorithm that triggers topological sector jumps during the assembly of Markov chain of lattice configurations. We study its...
We review recent theoretical developments concerning the definition and the renormalization of equal-time correlators that can be computed on the lattice and related to Parton Distribution Functions (PDFs) through a factorization formula. We focus on the theoretical aspects in the context of a scalar field theory.
We apply a novel method to a non-perturbative determination of the hadronic form factors describing the exclusive semileptonic $B \to D^{(*)} \ell \nu_\ell$ decays. The method is based on the non-perturbative calculation of the dispersive bounds due to unitarity and analyticity, and it allows to determine in a model-independent way the form factors in the full kinematical range of the recoil,...
I will present lattice investigations into the thermal phase structure of the Berenstein--Maldacena--Nastase deformation of maximally supersymmetric Yang--Mills quantum mechanics. The phase diagram of the theory depends on both the temperature $T$ and the deformation parameter $\mu$, through the dimensionless ratios $T / \mu$ and $g = \lambda / \mu^3$ with $\lambda$ the 't Hooft coupling. We...
Flow models are emerging as a promising approach to sampling complicated probability distributions via machine learning in a way that can be made asymptotically exact. For applications to lattice field theory in particular, success has been demonstrated in proof-of-principle studies of scalar theories, gauge theories, and thermodynamic systems. This work develops approaches which enable...
Generalized parton distributions (GPDs) are among the most fundamental quantities for describing the internal structure of hadrons, providing information about the momentum and spatial distributions of quarks and gluons. Exclusive scattering processes offer a natural framework to extract GPDs from experiments. However, the exclusivity of the process and their indirect relation to the...
In this talk we present results from numerical simulations of $\mathcal{N}$ = 4 super Yang-Mills for two color gauge theory over a wide range of ’t Hooft coupling $0 < \lambda ≤ 30$ using a supersymmetric lattice action. Numerical study of this lattice theory has been stymied until recently by both sign problems and the occurrence of lattice artifact phases at strong coupling. We have recently...
Experimental precision for measurements of $B$ meson decays will continue to improve over the coming years as Belle II collects more data and the LHC returns to operation after its upgrade period. Independent measurements of $V_{ub}$ will soon be possible using rare $B\to\tau\nu$ decays, for which $B$ meson decay constants $f_B$ are a key input.
We present updates from UKQCD/QCDSF/CSSM on...
We provide the generalization of the formalism needed to relate the three-particle
finite-volume spectrum to infinite-volume scattering amplitudes for the case of three nondegenerate scalar particles with arbitrary masses. The results can be expressed in a form similar to those for identical particles, except for the addition of an extra flavor index. We do so using a simplified method in...
Mass-split models are governed by a nearby conformal infrared fixed point and therefore feature by construction a large separation of scales. This makes them attractive candidates to explore beyond the standard model scenarios describing the Higgs boson as a composite particle. We report updates on our investigation based on an SU(3) gauge theory with four light and six heavy flavors in the...
We propose a continuous differentiable and invertible gauge field transformation parametrized with neural networks. We apply this technique to 2D U(1) pure gauge system, combine the transformation and HMC, and train the neural network field transformation for improved tunneling of topological sectors during the gauge generation. We present the properties of the trained transformation applied...
During recent years there has been a tremendous and exciting activity which aims at calculating the full x-dependence of parton distributions (PDFs) and related quantities in lattice QCD. To this end one needs to compute Euclidean correlators which through a perturbative matching procedure can be related to the light-cone correlation functions of interest. While the matching has already been...
The past several years have seen significant progress in the theoretical developments for interpreting three-particle finite-volume energies. The successful application of these frameworks using lattice data for three-pion and three-kaon systems with maximal isospin has been demonstrated from several groups using a modest set of energies to constrain the three-particle interactions. Here we...
The non-perturbative part of the cross-section of high-energy processes may be expanded in terms of the process's large energy scale. This gives rise to a tower of distribution functions, labeled by their twist (mass dimension minus spin). The leading twist (twist-2) contributions have been at the center of experimental measurements, theoretical investigations, and lattice QCD calculations. It...
Semileptonic Bs to K and Bs to Ds decays provide additional channels to determine the CKM matrix elements |Vub| and |Vcb| or to investigate lepton flavour universality violation in R-ratios comparing decays with heavy or light final state leptons. We calculate the decay form factors using domain-wall light, strange and charm quarks, with the Columbia formulation of the RHQ action for the...
In this talk, we present a lattice study of the scattering of pseudo-Goldstone Bosons in SU(3) gauge theory with $N_f=8$ light Dirac fermions, a theory which lies close to the boundary of the conformal window. The scattering phase shift is measured in the s-wave, maximal isospin channel for different values of the scattering momentum, as well as for different values of the underlying fermion...
We present the first determination of the universal parameters of the a1(1260) from QCD. This consists of three steps presented in the talk:
(1) Lattice QCD calculation including three-meson operators; (2) Generalization of three-body quantization condition including sub-systems with spin and coupled channels; (3) Analytic continuation of the infinite-volume amplitude and determination of the...
Flow-based models were previously successfully applied for the generation of configurations in lattice (gauge) field theories in two dimensions. In this work, we discuss further development of this approach for lattice gauge theories in four dimensions. We show several implementations and apply improvements to the approach. We study different masking patterns and choices of frozen loops, as...
The magnetic polarisability of the pion is calculated at a range of quark masses using the background field method. These results are facilitated by the use of the background-field corrected clover fermion action which removes the unphysical quark mass renormalisation due to the Wilson term in a background magnetic field. A magnetic-field dependent quark-propagator projector enables the ground...
Our charm program uses a mixed action with twisted-mass valence quarks over non-perturbatively improved Wilson sea quarks, in order to study various quantities in a relativistic and manifestly local framework of full QCD. The sea sector consists of $N_f=2+1$ ensembles generated by the CLS initiative. Thanks to open boundary conditions, this offers access to fine ensembles without topological...
We review dilaton chiral perturbation theory (dChPT), the low-energy theory for the light sector of near-conformal, confining theories. dChPT accounts for the pions and the light scalar,and provides a systematic expansion in both the fermion mass and the distance to the conformal window. Unlike ChPT, dChPT predicts a large-mass regime in which the theory exhibits hyperscaling,while the...
Critical slowing down presents a critical obstacle to lattice QCD calculation at the smaller lattice spacings made possible by Exascale computers. Inspired by the concept of Fourier acceleration, we study a version of the Riemannian Manifold HMC (RMHMC) algorithm in which the canonical mass term of the HMC algorithm is replaced by a rational function of the gauge-covariant, QCD Laplace...
Much of the resonant spectrum of QCD consists of states which decay strongly into two- and three-body final states. Lattice QCD calculations have matured to the stage where these states can be reliably resolved in first principles numerical calculations. While connecting these finite-volume results to infinite-volume scattering is now commonplace in the two-body sector, three-body physics...
Electric and magnetic polarizabilities are two of the fundamental properties of hadrons which help us understand the distribution of charge and currents inside hadrons and how they respond to external electromagnetic fields. For nucleons, these values are determined experimentally from Compton scattering. For charged pions, the experiments are more challenging since no free pion target is...
For an asymptotically free theory, a promising strategy for eliminating Critical Slowing Down (CSD) is naïve Fourier acceleration. This requires the introduction of gauge-fixing into the action, in order to isolate the asymptotically decoupled Fourier modes. In this talk, we present our approach and results from a gauge-fixed Fourier-accelerated hybrid Monte Carlo algorithm, using an action...
We calculate the low-energy constant $L_{10}$ in an SU(4) lattice gauge theory
with dynamical fermions in two representations. This theory is close to a particular composite-Higgs model. From this, we obtain the contribution of the new strong sector to the S parameter. The resulting upper bound on the vacuum misalignment parameter $\xi$ is similar to current estimates for this bound. We...
We present the status of a project to calculate $D \rightarrow \pi \ell \nu$, $D \rightarrow K \ell \nu$ and $D_s \rightarrow K \ell \nu$ semileptonic form factors with 2+1f Domain Wall Fermions for both heavy and light quarks. We plan to cover the full kinematic range and three point functions are being computed on the RBC-UKQCD Iwasaki gauge ensembles. Given the exponential growth of noise,...
We consider three-particle systems consisting of two identical particles and a third that is different, with all being spinless, e.g. $\pi^+ \pi^+ K^+$. We generalize the formalism necessary to extract two- and three-particle infinite-volume scattering amplitudes from the spectrum of such systems in finite volume. We use a relativistic formalism based on an all-orders diagrammatic analysis in...
Strong interactions produce a rich spectrum of resonances which decay into three or more hadrons. Understanding their phenomenology requires a theoretical framework to extract parameters from experimental data and lattice QCD simulations of hadron scattering. Two classes of relativistic three-body approaches are currently being pursued: the EFT-based and unitarity-based one. We consider a...
We introduce LeapfrogLayers, an invertible neural network architecture that can be trained to efficiently sample the topology of a 2D U(1) lattice gauge theory. We show an improvement in the integrated autocorrelation time of the topological charge when compared with traditional HMC, and propose methods for scaling our model to larger lattice volumes.
We present a new method aiming at a non-perturbative, model-independent determination of the momentum dependence of the form factors entering hadronic semileptonic decays using unitarity and analyticity constraints. We extend the original proposal of Ref. [1] and, using suitable two-point functions computed non-perturbatively, we determine the form factors at low-momentum transfer $q^2$ from...
In the context of possible dilaton behavior in near conformal gauge theories, it has recently been proposed that a parametrized potential $V_\Delta$, interpolating between two limiting forms, might effectively describe the light particle spectrum. We tested two models, namely SU(3) gauge theory with $N_f = 8$ fermions in the fundamental rep or $N_f = 2$ fermions in the sextet rep, against this...
We present new results on heavy meson semileptonic decays using the highly improved staggered quark (HISQ) action for both valence and 2+1+1 sea quarks. The use of the highly improved action, combined with the MILC collaboration's gauge ensembles with lattice spacings down to ~0.042 fm, allows the b quark to be treated with the same discretization as the lighter quarks. This unified treatment...
The light-cone distribution amplitude (LCDA) of the pion carries information about the distribution of its quarks, which is an important input to various experiments. We present our proof-of-concept lattice calculation of the second Mellin moment of the LCDA using the heavy quark operator product expansion (HOPE) method. Our computation shows agreement with complementary methods of...
We study decuplet baryons from meson-baryon interactions. We report the analysis of the P-wave $\pi N$ interaction with isospin $I=3/2$ and the $\bar{K}\Xi$ interaction with $I=0$, which have channels to a $\Delta$ and $\Omega$ baryon, respectively. The interaction potentials are calculated in the HAL QCD method using 3-quark-type source operators at $m_{\pi} \approx 410~\text{MeV}$. We use...
We have proposed a concrete experimental setup for quantum simulating the $(1+1)$-dimensional Abelian Higgs model in J. Zhang et al. (2018), where the Hamiltonian in the electric field representation can be implemented on a multi-leg ladder with a single atom in each rung. The finite-size scaling of the energy gap can be measured and its universal behavior can be extracted at large enough...
We present various applications of the gradient-flow beta-function, including an extended study of the finite-volume version in the $N_f = 10$ fundamental rep SU(3) model, prompted by claims of possible conformality. We show how the infinite-volume beta-function can be reached through a sequence of stages, handling the correlation across gradient-flow time when taking the continuum limit, and...
A very rich place to look for phenomena to challenge our current understanding of physics is the flavor sector of the Standard Model (SM). In particular, the $V_{cb}$ matrix element of the CKM matrix is the subject of a long standing tension, depending on whether it is determined using inclusive or exclusive methods. On top of that, the current average of $R(D^\ast)$ shows a 3$\sigma$ tension...
The hyperon-nucleon interaction with the strangeness $S=-1$ region is complicated and difficult to investigate because its flavor sector involves all the irreducible representation except the flavor singlet and has the worst signal-to-noise ratio among the Strangeness regions [1-2]. Some efforts to overcome such difficulties will be discussed.
References:
[1] H. Nemura et al., AIP...
The tensor network framework is an alternative to traditional lattice-based methods where one can simulate the statics as well as dynamics of lattice gauge theories (LGTs) without encountering the sign problem.
So far, however, most tensor network studies of non-abelian LGTs have been restricted in scope to one spatial dimension with open boundary conditions.
This restriction is lifted in...
The RG beta function describes the running of the renormalized coupling and connects the ultraviolet and infrared regimes of quantum field theories. We consider both the finite volume step scaling and the continuous beta function of the gradient flow coupling in SU(3) systems with fundamental fermions. Investigating theories with $N_f=6$, 8, 10 and 12 flavors allows us to study the onset of...
The baryon-baryon interaction in the strangeness =-1 channel was recently analysed by using the lattice QCD data near the physical point combined with the HAL QCD method [1]. In the present contribution, we show our first attempt to extract the coupled-channel NΛ-NΣ potential from thesame data by using the Misner's method which is known to be a reliable way to perform the partial wave...
We study baryon-baryon scattering with Luscher’s method for N_c = 4 gauge theory. To improve signal in our scattering observables, we employ the Laplacian Heaviside or Distillation method to construct low rank interpolating operators with good overlap with low lying energy states. Though of interest for large N_c QCD studies, the LSD collaboration has been investigating a dark matter candidate...
This talk will report recent results from ongoing calculations of the $D\to\pi$ semileptonic decay by the Fermilab lattice and MILC collaborations. Our calculation employs the HISQ action for both sea and valence quarks and includes several ensembles with physical-mass up, down, strange, and charm quarks and lattice spacings ranging from 0.15 fm down to 0.06 fm. At each lattice spacing, an...
We present the first lattice QCD calculation of the distribution amplitudes of longitudinally and transversely polarized vector mesons K∗ and φ using large momentum effective theory. We use the clover fermion action on three ensembles with 2+1+1 flavors of highly improved staggered quarks (HISQ) action, generated by MILC collaboration, at physical pion mass and {0.06, 0.09, 0.12} fm lattice...
The classical O(2) model is the zero-gauge-coupling limit of compact scalar quantum electrodynamics in Euclidean spacetime. We obtain two dual representations of the O(2) model, where the field quantum numbers on the plaquettes determine the charge quantum numbers on the links according to Gauss's law. Taking the time continuum limit, we study the Hamiltonians in the two representations with a...
The $q$-state clock model is a classical spin model that corresponds to the Ising model (when $q= 2$) and the XY model (when $q\rightarrow\infty$). The integer-$q$ clock model has been studied extensively and has been shown to have a single phase transition when $q = 2,3,4$ and two phase transitions when $q > 4$.We define an extended-$q$ clock model that reduces to the ordinary $q$-state clock...
We present our current progress on the lattice calculation of decay constants for $B_{(s)}$, $D_{(s)}$ mesons using sequential Bayesian method and the Oktay-Kronfeld (OK) action for the charm and bottom quarks (valence quarks). Here, the masses of charm and bottom quark are determined non-perturbatively. For the light spectator quarks (up, down and strange), we use HISQ action. Lattice...
The dynamics of the glueballs is important in the context of their experimental search as well as for understanding non-Abelian theories. The glueballs of the dark SU(N) Yang-Mills theory are also good candidates of the dark matter [1,2].
The low energy effective Lagrangian of the 0++ glueball may be determined from the interglueball potential calculated on lattice. In this talk, we report on...
We will present lattice QCD results for x-dependent distribution amplitudes for pion and kaon. The computations were carried out using valence Wilson Clover fermions on HISQ gauge configurations with 2+1 flavors, all with physical values of pion and kaon masses and at a lattice spacing of 0.076 fm. Computations used hadrons states boosted up to a momentum of 1.7 GeV. To arrive at the results...
Numerical estimation of fermionic observables often requires introduction of auxiliary bosonic fields that have no direct physical relevance through a Hubbard-Stratonovich transformation. The variance of some fermionic observables (for example, appropriately constructed local four-fermion operators in 2d Gross-Neveu model) when they estimated using such auxiliary fields may not correspond to...
It has been recently shown how explicit low-storage Lie group integrators can be built from classical low-storage methods of Williamson's type. We discuss a one-parameter family of three-stage third-order methods and show how a coefficient scheme can be chosen specifically for optimal integration of the gradient flow. We also illustrate how two low-storage fourth-order integrators can be used...
We use a regular tessellation of AdS$_2$ based on the (2,3,7) triangle group, with an extension to Euclidean AdS$_3$, to study
the AdS/CFT correspondence. Perturbative calculations are verified and initial tests of monte carlo calculations for
non-perturbative $\phi^4$ theory exhibit critical phenomena on the boundary.
We have completed a lattice QCD calculation of $\Delta m_K$, the mass difference between the long- and short-lived K mesons. The calculation was performed on a $64^3 \times 128$ lattice using 152 configurations with physical quark masses and an inverse lattice spacing of $a^{-1}=2.36$ GeV. While the statistical error approaches a relatively small size of 9%, several sources of systematic...
In this talk, we report the rho resonance study using the HAL QCD method. We calculate the $I=1$ $\pi \pi$ potential at $m_{\pi} \approx 410$ MeV by a combination of the one-end trick, sequential propagator and covariant approximation averaging (CAA). Thanks to those techniques, we determine the non-local $I=1$ $\pi\pi$ potential at the next-to-next-to-leading order (N$^2$LO) of the derivative...
We present regression and compression algorithms for lattice QCD data utilizing the efficient binary optimization ability of quantum annealers. In the regression algorithm, we encode the correlation between the independent and dependent variables into a dictionary optimized for sparse reconstruction. The trained correlation pattern is used to predict lattice QCD observables of unseen lattice...
Determining the standard model prediction for the decay amplitude of a long-lived neutral kaon into two photons is an important step toward the goal of calculating the two-photon contribution to $K_L\to\mu^+\mu^-$ decay. In this talk we will describe a computational strategy to determine this decay amplitude using lattice QCD. While the lattice QCD calculation is carried out in finite...
We propose a method to extract the HAL QCD potential from correlation functions with non-zero total momentum (boosted system). After brief explanation of the formulation with non-zero total momentum ($P$), we apply it to the $I=2$ $\pi\pi$ system. Using 2+1 flavor PACS-CS configurations at $m_\pi=700$ MeV and $a=0.09$ fm on $32^3x64$ lattice, we calculate the $I=2$ $\pi\pi$ potential with...
Previous work has shown that renormalization group blocking of a
2+1 flavor DWF ensemble with 1/a = 2 GeV can produce an ensemble
with 1/a = 1 GeV, with physical quantities on the blocked 1 GeV
ensemble within a few percent of their values on an independently
generated 1 GeV ensemble. This has led us to investigate using the
blocked ensemble DWF operator as a coarse-grid operator for...
We study the two-dimensional Yang-Mills theory with four supercharges in the large N limit. By using thermal boundary conditions, the distribution of scalars is studied at large N, in the limit of a vanishing scalar potential. We explore the extent of scalar distribution in this theory and look for behavior identical to its maximally supersymmetric cousin, which is known to admit holographic...
We present a calculation of the proton momentum and angular momentum decomposition using overlap fermions on a 2+1-flavor RBC/UKQCD domain-wall configuration at around 171 MeV which is close to the physical pion mass. A complete determination of the momentum and angular momentum fractions carried by up, down, strange and glue inside proton has been done with valence pion masses varying from...
I review multigrid algorithms for domain wall fermions and discuss the development status of a domain decomposed hybrid monte carlo appropriate for chiral fermions and tailored for use on GPU accelerated computing nodes.
Self-interacting scalar quantum field theories possessing PT-symmetry are physically admissible since their energy spectrum is real and bounded below. However, models with PT-invariant potentials can have complex actions in general. Thus, they cannot be studied using methods based on traditional Monte Carlo due to a sign problem. We use complex Langevin dynamics to study two-dimensional...
A pair of triply charmed baryons, $\Omega_{ccc}\Omega_{ccc}$, is studied as an ideal dibaryon system by (2+1)-flavor lattice QCD with nearly physical light-quark masses and the relativistic heavy quark action with the physical charm quark mass. The spatial baryon-baryon correlation is related to their scattering parameters on the basis of the HAL QCD method. The $\Omega_{ccc}\Omega_{ccc}$ in...
In recent years, the lattice effective field theory, a lattice stochastic methods, were successfully applied in solving the nuclear many-body problems. It has shown great advantages in simulating from first principles the atomic nuclei at ground state and excited states, nuclear scattering and reaction, nuclear matter at zero and finite temperature, etc. In this talk, I will give a brief...
In this joint venture between mathematicians and physicists, we develop efficient recursive strategies to tackle a class of high dimensional integrals having a special product structure with low order couplings, motivated by models in lattice gauge theory. A novel element of this work is the potential benefit in using a family of numerical integration methods called "lattice cubature rules"....
The Atiyah-Singer(AS) index theorem on a closed manifold is well understood and appreciated in physics. On the other hand, the Atiyah-Patodi-Singer(APS) index, which is an extension to a manifold with boundary, is physicist-unfriendly, in that it is formulated with a nonlocal boundary condition. Recently we (3 physicists and 3 mathematicians) proved that the same index as APS is obtained from...
The tensor renormalization group (TRG) is a promising approach to study various models of lattice field theory.
In particular, we can easily realize numerical calculations
for theories with the sign problem, and on extremely large volume lattices, by the method. In this talk, I will review the recent progress in the TRG method.
We present results for the photon emission rate determined from the transverse channel vector correlator at fixed spatial momentum using two-flavor dynamical Wilson fermions at T ~ 250 MeV. We estimate the transverse channel spectral function using the continuum extrapolated correlator by applying various fit ansätze with a smooth matching to the NLO perturbative result. We confront our...
The estimation of the Källén-Lehmann spectral density from gauge invariant lattice QCD two point correlation functions is proposed, and explored via an inversion strategy based on Tikhonov regularisation. As proof of concept the SU(2) glueball spectrum for the quantum numbers $J^{PC}=0^{++}$ is investigated, for various values of the lattice spacing, using the published data of...
The decoupling strategy by the ALPHA collaboration uses simultaneous decoupling of $N_{\rm f}=3$ heavy quark flavours to obtain a controlled connection between the $\Lambda$-parameters in QCD with $N_{\rm f}=3$ and $N_{\rm f}=0$ quark flavours, respectively, in terms of a common decoupling scale. Corrections are either power suppressed in the heavy quark mass, or perturbatively suppressed by...
Graphene can be modeled by the Hubbard model on a honeycomb lattice. However, this system suffers strongly from the sign problem if a chemical potential is included.
Tensor network methods are not affected by this problem. We use the imaginary time evolution of a fermionic Projected Entangled Pair State, which allows to simulate both parity sectors independently. Incorporating the fermionic...
Composite Higgs models can be extended to the Planck scale by means of the partially unified partial compositeness (PUPC) framework. We present in detail the Techni-Pati-Salam model, based on a renormalizable gauge theory SU(8)×SU(2)L×SU(2)R. We demonstrate that masses and mixings for all generations of standard model fermions can be obtained via partial compositeness at low energy, with...
The photon emissivity of quark-gluon plasma probes the interactions in
the medium and differs qualitatively between a weakly coupled and a
strongly coupled plasma in the soft-photon regime. The photon
emissivity is given by the product of kinematic factors and a spectral
function associated with the two-point correlator of the
electromagnetic current at lightlike kinematics. A certain...
We report on the first master-field simulations of QCD with 2+1 dynamical quark flavours using non-perturbatively improved stabilised Wilson fermions. Our simulations are performed at a lattice spacing of 0.095 fm with 96 and 192 points in each direction. With $Lm_\pi$=12.5 and 25, both lattices feature a pion and kaon mass of about 270 and 450 MeV. This setup is compatible with a chiral...
We present analysis details and new results for the strong coupling $\alpha_s(m_Z)$, determined by the decoupling strategy detailed in the previous talk. Starting from a line of constant physics (LCP) from previous ALPHA Collaboration work, we simulate $N_f=3$ massless quarks to measure a set of renormalization and improvement constants which allow us to determine the simulation parameters for...
Among novel strong interactions beyond the standard being currently investigated, the Sp(4) gauge theory with two fundamental and three antisymmetric fermions is compatible with the pseudo-Nambu-Goldstone-Boson (pNGB) mechanism of electroweak symmetry breaking and the implementation of partial top compositeness. Unlike in QCD, the lack of a manifest experimental counterpart and the scarcity of...
We applied tensor network methods to study strongly coupled U(N) in its dimer formulation. We investigated the chiral condensate as a function of the quark mass and the degree of the symmetry group, and find good agreement with Monte Carlo simulations.
We present our results on the study of the electromagnetic conductivity in
dense quark-gluon plasma obtained within lattice simulations with $N_f = 2 + 1$
dynamical quarks. We employ stout improved rooted staggered quarks at
the physical point and the tree-level Symanzik improved gauge action.
The simulations are performed at imaginary chemical potential and the
Backus-Gilbert method is...
The QCD-coupling is a necessary input in the computation of many observables, and the parametric error on input parameters can be a dominant source of uncertainty. The coupling can be extracted by comparing high order perturbative computations and lattice evaluated moments of mesonic two-point functions with heavy quarks, which provide a high energy scale for perturbation theory. The...
We study a four-dimensional lattice gauge theory with fermions transforming as the fundamental and antisymmetric representations of Sp(2N) gauge groups. More specifically, we consider the case of N=2 with two and three Dirac flavors for the fundamental and antisymmetric fermions, respectively, whose continuum limit serves as the microscopic theory for SU(4)/Sp(4) models of composite Higgs and...
We calculate the free energy of the CP(1) model with a topological term using the tensor renormalization group (TRG) method. TRG calculations allow to use large volumes and to determine the phase structure in the presence of the topological term. In this talk, we will focus on the systematic errors appearing in the calculations and compare our results to previous work. Our TRG calculations...
In this talk we show our lattice QCD calculations for the sphaleron rate (the Minkowski rate for topological charge diffusion). It is determined by modeling the spectral function encoded in the Euclidean topological-charge-density two-point function. The Euclidean correlation functions are measured under gradient flow to reduce noise with improved operators which can more accurately measure...
Minimally doubled fermions, have been proposed as lattice fermions which preserve chiral symmetry and being strictly local too. In our previous works, we have studied how the broken hypercubic symmetry of Boriçi - Creutz fermions affect the light hadrons spectrum, have proposed a method of how to restore it and also made a simple test on the pion mass using the corrected action. In this work...
We perform dynamical lattice studies for mesonic spectroscopy of Sp(4) gauge theory coupled to three flavours of Dirac fermions in the antisymmetric representation. In addition, mesons composed of valence fundamental Dirac fermions are considered in the partially-quenched setting. We employ the Wuppertal and APE smearing methods to improve the signals of effective masses. By combining the...
For many physical systems, the computation of observables amounts to solving an integral over a strongly oscillating complex-valued function. This so-called sign problem renders the numerical evaluation of these integrals a hard computational problem. Complex Langevin dynamics is one numerical method for tackling the sign problem. In this talk, I introduce a generalized framework for this...
Motivated by studies of Composite Higgs models based on the $SU(4)/Sp(4)$ coset on the one hand and by large-$N$ limit investigations on the other, we analyse the quenched meson spectrum of Symplectic -- $Sp(2N)$ -- gauge theories on the lattice. We examine fermions in the symmetric representation of $Sp(4)$; we also study fermions in the fundamental, antisymmetric and symmetric...
Multilevel techniques in lattice were introduced twenty years ago by Lüscher and Weisz as a way to overcome exponential signal-to-noise decay in lattice gauge theory. It is known that the algorithm performs well when the correlation length of the system is small, and less favourably when it is large. In this project, the transition between these regimes is studied. The 2D-Ising Model is used...
Non-perturbative renormalization of composite operators can be achieved by combining the step-scaling method with an intermediate finite volume renormalization scheme. Matching to low energy physics requires that the finite volume scheme can be accurately evaluated at the bare couplings used in simulations of hadronic physics.
In this regime, the gradient flow for the gauge field has been...
We present a determination of the gradient flow scales $w_0$, $\sqrt{t_0}$ and $t_0/w_0$ in isosymmetric QCD, making use of the gauge ensembles produced by the Extended Twisted Mass Collaboration (ETMC) with $N_f=2+1+1$ flavours of Wilson-clover twisted-mass quarks including configurations close to the physical point for all dynamical flavours. The simulations are carried out at three values...
We extract the heavy quark diffusion coefficient $\kappa$ and the resulting momentum broadening $\langle p^2 \rangle$ of a heavy quark embedded in a far-from-equilibrium gluon plasma using classical-statistical lattice simulations. We find several features in the time dependence of the momentum broadening: a short initial rapid growth of $\langle p^2 \rangle$, followed by linear growth with...
We discuss the theoretical foundations of non-equilibrium Monte Carlo simulations based on Jarzynski's equality and present, as an example of application, the determination of the running coupling in the Schrödinger-functional scheme.
The heavy quark diffusion coefficient is encoded in the spectral
functions of the chromo-electric and the chromo-magnetic correlators that are
calculable on the lattice. We study the chromo-electric and the chromo-magnetic correlator in the deconfined phase of SU(3) gauge theory using Symanzik flow at
two temperatures 1.5Tc and 10000Tc, with Tc being the phase transition
temperature. To...
We present a method to improve the lattice effective field theory description of the shape of atomic nuclei by applying unitary transformations to the Hamiltonian. The employed unitary operator is constructed as a reflection transformation from the original and the desired wave function. Similarly to a derivative expansion, it can be improved systematically so that one can tune the $\langle...
We present a calculation of the QCD renormalization constants (RCs) for quark bilinear operators, evaluated non-perturbatively on the lattice in the RI'-MOM scheme. The calculation is performed by using dedicated ensembles with $N_f=4$ degenerate dynamical twisted mass (clover) fermions and the Iwasaki gauge action. A detailed analysis is reported, with emphasis on the control or subtraction...
$Sp(2N)$ gauge theories are potentially relevant in the context of Composite Higgs Models and provide an alternative sequence to the more widely studied $SU(N)$ and $SO(N)$ groups in the investigation of the large-N limit of Yang-Mills theories.
In this contribution, we report on our study of the scale setting and of the topological features of the vacuum of $Sp(2N)$ lattice (pure) gauge...
Heavy quark transport coefficients calculated from first-principles QCD are a crucial input for transport models. Utilizing the heavy quark limit, we will discuss the results of a novel approach to nonperturbatively estimate the heavy quark diffusion coefficient in a hot gluonic medium from gradient-flowed color-electric correlators on the lattice. Unlike others, this approach can be extended...
We determine non-perturbatively the renormalization constant of the flavour-singlet local vector current with $O(a)$-improved Wilson fermions in a moving reference frame. The renormalization constant is fixed by comparing the expectation values (one-point function) of the local vector current and of the conserved one in thermal QCD with a non-zero imaginary chemical potential and in the chiral...
Back in 2000, Lellouch and Lüscher derived a formula, relating the
matrix element of the weak $K \rightarrow 2\pi$ decay in a finite
volume to its infinite-volume counterpart.
In contrast, albeit latest theoretical developments enable the
extraction of three-body scattering amplitudes on the lattice,
a three-particle analog of the Lellouch-Lüscher equation has not
been available until...
We investigate a UV completion of a pseudo-Goldstone Composite Higgs model based on a SU(2) gauge theory with two fundamental flavours of Dirac fermions. The model is based on the SU(4) to Sp(4) chiral symmetry breaking pattern and can be view as a minimal template to explore the phenomenological signatures of Composite Higgs models. To characterize the model, lattice calculations are used to...
To facilitate future efficient calculation of the connected and disconnected parts of the vector-vector correlator and other observables in QCD+QED with C* boundary conditions, dilution and distillation noise reduction techniques were implemented into the OpenQxD program. To find the low-lying eigenmodes of the gauge-covariant Laplacian that form the distillation sub-space, the PRIMME...
We study the static energy between a quark anti-quark pair in a thermal medium based on ensembles with $N_f=2+1$ dynamical HISQ flavors. Our dataset spans the phenomenologically relevant temperature range between T=140MeV-2GeV based on lattice sizes $48^3$x10,12 and 16. The real- and imaginary part of the potential is determined from the spectral function of Wilson-line correlators in Coulomb...
Motivated by recent scenarios of exotic infrared behaviour and by earlier lattice findings, we present results for the $\mathrm{SU}(2)$ gauge theory with one Dirac flavor in the adjoint representation. This provides a major update on our previous investigation of this theory, including data for four values of the gauge coupling $\beta$, and for smaller masses and larger volumes than previously...
Many candidate theories for BSM physics involve Yang-Mills gauge fields coupled to scalars. By considering a 'toy model' of a GUT — an SU(3) gauge theory with a scalar 'Higgs' in the fundamental representation — we give analytical reasons to suspect qualitative discrepancies between the spectrum obtained from the conventional perspective of spontaneous gauge symmetry breaking compared to an...
It is common practice to truncate the finite-volume formula for K to pi pi, and other one to two transitions, to only include the lowest partial wave, as in the original derivation by Lellouch and Lüscher. However, as the precision of lattice calculations increases, it may become important to asses the systematic effect of this approximation. With this motivation, we compare the S-wave-only...
OpenQ$^\ast$D code has been used by the RC$^\ast$ collaboration for the generation of fully dynamical QCD+QED gauge configurations with C$^\ast$ boundary conditions. In this talk, optimization of solvers provided with the openQ$^\ast$D package relevant for porting the code on GPU-accelerated supercomputing platforms is discussed. We present the analysis of the current implementations of the...
We present an update of the scale setting for $N_f=2+1$ flavor QCD using gradient flow scales and pseudoscalar decay constants. We analyze the latest ensembles with $2+1$ flavors of non-perturbatively improved Wilson fermions generated by CLS for improved precision. Special care is taken to correct for mistuning by measuring directly the mass derivatives of the various observables. We...
We have studied finite temperature complex static quark-antiquark potential for 2+1 flavor QCD using highly improved staggered action with pion mass 161 MeV. We extracted the potential using the Wilson line correlator fixed in Coulomb gauge. For the extraction, we have used a newly developed method [1] of splitting the correlator into symmetric and anti-symmetric parts. Using this method we...
Radiative transitions between stable hadrons and hadronic resonances can provide valuable insights into the composition of hadronic resonances. In this talk, we present a toy-model investigation regarding the feasibility of realistic lattice QCD calculations of reactions where a stable hadron undergoes a transition to one of several two-hadron channels. We describe the coupled-channel...
In GUT-like scenarios it is necessary to break the gauge group to the SM-group. This is usually achieved by adding scalars to the theory, which may introduce one or more possible breaking patterns to the theory. Additionally, a valid description of gauge-symmetry-breaking needs to be manifestly gauge-invariant, which is often neglected in standard phenomenology.
In our work we therefore...
Recently a method of measuring static force from the lattice using an insertion of chromoelectric field to an Wilson loop has been proposed to tackle the ambiguities of taking numerical derivative of the static potential. We present the current status of testing the viability of this approach and also expand the calculation for the first time to use gradient flow, which solves the problems...
We report our calculation of the inter-quark potential of bottomonium at non-zero temperature using the HAL QCD method. This is applied to NRQCD non-local correlation functions generated from anisotropic FASTSUM ensembles. The correlation functions are initially calculated in momentum space for greater efficiency. Results will be presented for the interquark potential of various states as a...
Lattice QCD simulations directly at physical masses of dynamical light, strange and charm quarks are highly desirable in order to remove systematic errors due to chiral extrapolations. However such simulations are still challenging. We discuss the adaption of efficient algorithms, like higher order integrators or multi-grid methods, within the molecular dynamics of the Hybrid Monte Carlo...
Algebraic multigrid methods have become state of the art at solving discretizations of the Dirac equation in Lattice QCD, in particular, when systems are ill-conditioned. Lattice QCD is bound by the use of supercomputers to speed up their simulations, where algebraic multigrid methods have brought a way of pushing the computational boundaries at large-scale and they open the possibility of...
An exotic hybrid meson resonance appearing in $J^{PC}=1^{-+}$ is determined for the first time from lattice QCD. Many finite volume energy levels are computed and used with the coupled-channel extension of the Lüscher formalism to determine the scattering amplitudes in the limit where SU(3) flavour symmetry is exact. The scattering amplitude contains a pole that has a large coupling to an...
We present the Backus-Gilbert method as a means of reconstructing spectral functions from NRQCD meson correlator data at non-zero temperature. We focus in particular on the resolving power of the method, providing a demonstration of how the underlying resolution functions can be probed by exploiting the Laplacian nature of the NRQCD kernel. We conclude with estimates of the bottomonium ground...
The naturalness problem in the Higgs sector finds a popular solution in composite Higgs models. In such theories the Higgs boson emerges as the pseudo-Nambu-Goldstone boson associated with the breaking of a global symmetry realised in a new, strongly interacting sector. In this talk we address a model arising in this context and well motivated by phenomenological arguments, a SU(4) gauge...
At physical light quark masses, efficient linear solvers are crucial for carrying out the millions of inversions of the Dirac matrix required for obtaining high statistics in quark correlation functions. Adaptive algebraic multi-grid methods have proven to be very efficient in such cases, exhibiting mild critical slowing down towards very light quark masses and outperforming traditional solver...
In various theories of strongly-interacting dark matter non-degenerate flavors play an important role to satisfy constraints like relic abundance. To quantify the impact we investigate a candidate theory, Sp(4) gauge theory with two fundamental flavors. At the relevant quark mass scales we find interesting patterns in the pseudoscalar and vector channel, which mix behavior from chiral and...
We analyse the leading logarithmic corrections to the $a^2$ scaling of lattice artefacts in QCD, following the seminal work of Balog, Niedermayer and Weisz in the O(n) non-linear sigma model. Limiting to contributions from the action, the leading logarithmic corrections can be determined by the anomalous dimensions of mass-dimension 6 operators. These operators form a minimal on-shell basis of...
We present calculations of form factors and radiative transitions in the low-lying charmonium sector using Lattice QCD. Results for $J/\psi \to \eta_c \gamma$, $\chi_{c0} \to J/\psi \gamma $ partial widths are presented alongside other experimentally unobservable form factors. Comparisons are given to previous results in both lattice and experimental studies. Studying radiative transitions...
We discuss results for bottomonium at nonzero temperature obtained using NRQCD on FASTSUM Generation 2L ensembles. We give an update on results for spectral functions obtained using Kernel Ridge Regression, paying in particular attention to the generation of training data. We compare our findings to estimates of masses of both ground- and the first excited states obtained using multi-exponential fits.
We compute the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon. The calculations are performed using four flavors of stout smeared staggered quarks, with quark masses at their physical values. The continuum limit is taken using six different lattice spacings ranging from $0.132\,\text{fm}$ down to $0.064\,\text{fm}$. All strong isospin...
In this talk I will review some of the trends in computing systems
including discussing the new and upcoming systems in the U.S. and elsewhere as information allows. I will also discuss some of the programming models to develop software for these systems with an emphasis on portable, and where possible, performance portable approaches.
Attendees should create a DevCloud account using below link and event code before the session:
https://sforms.intel.com/DevCloud/?eventcode=lattice-07302021
Event Code: lattice-07302021
The session includes a giveaway of 10 Intel GPU developer platforms.
Join our virtual workshop on Essentials of Data Parallel C++ to learn about oneAPI which aims to provide a unified,...
This poster presents the results of the 2021 Lattice Diversity and Inclusion Committee survey.
