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...
The nature of the finite temperature phase transition in 2+1 flavor QCD depends
on the quark mass, and the order and universal class of the phase transition
are shown in a diagram called the Columbia plot.
The region of light quark masses in this diagram is not yet fully understood.
We present preliminary results of a three-flavor QCD study using Möbius-domain
wall fermions to search for...
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...
Measurements of flavour physics anomalies, such as those in the CKM matrix elements, rely on minimising systematic errors from the relevant parameters derived from experiment and theory. One method of determining $V_{ub}$ requires both $B\to\ell\nu$ branching fractions from experiment and $B$ decay constants from lattice QCD calculations, such as $f_B$ and $f_{B_s}$.
This work will present...
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...
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...
In this work, we take all the papers since 2000 that are classified as primary hep-lat to study whether there is any race or gender bias in the journal-publication process. We implement machine learning to predict the race and gender of authors based on their names, and look for measurable differences between publication outcomes based on author category.
We would like to invite discussion...
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...
We report our implemenation of the Field-Transformation HMC algorithm following Luescher's paper "Trivializing maps, the Wilson flow and the HMC algorithm". This algorithm has similar effects as the Riemannian Manifold HMC (RMHMC) algorithm. Comparing with the original HMC algorithm, improvement on the topology tunneling rate is observed when generating the pure gauge configurations.
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...
Neutrinoless double beta decay is a long-sought after process which would provide evidence of lepton number violation in our universe. Computing the rate from first principles requires non-perturbative input in the form of a nuclear matrix element which must be computed on the lattice. This poster will discuss the contribution to this matrix element from short-distance, dimension-9 operators....
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...
Interpolator constructions are a requisite tool for calculations in lattice quantum field theory. Better interpolating constructions lead to ground state dominance at earlier times, and thus less noise, making computations cheaper computationally. Various classical-computing methods exist to optimize interpolator constructions. In this work, we show that optimal interpolator constructions can...
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.
This poster presents the results of the 2021 Lattice Diversity and Inclusion Committee survey.
