The thermodynamics of strongly interacting matter in extreme conditions can be investigated via lattice QCD simulations. In this talk, I will give an overview of recent developments in this field, focusing on the impact of temperature, background electromagnetic fields as well as an isospin asymmetry between the light quark chemical potentials. Selected applications of the results for...
We present the most recent results from the FASTSUM collaboration for hadron properties at high temperature from anisotropic lattice QCD. This includes the temperature dependence of the light and charmed meson and baryon spectrum, as well as properties of heavy quarkonia.
In this talk we present our study of the electromagnetic conductivity in dense quark-gluon plasma obtained within lattice simulations with Nf = 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. To reconstruct electromagnetic conductivity...
The heavy quark diffusion coefficient is encoded in the spectral functions of the chromo-electric and the chromo-magnetic correlators, of which the latter describes the T/M contribution. We study these correlators in the deconfined phase of SU(3) gauge theory on the lattice using the gradient flow. We perform both continuum and zero flow time limits to extract the heavy quark diffusion...
We present results for the analysis of the energy and spectral width of the quark-antiQuark potential obtained from wilson line correlators at finite temperature using 2+1 flavor HISQ configurations ms/ml=20. We extract the energy and spectral width using 4 different methods: Zero temperature subtraction, Pade fit, Bayesian Reconstruction and HTL motivated fit. We compare the results and...
The magnetic fields generated in non-central heavy-ion collisions are among the strongest fields produced in the universe, reaching magnitudes comparable to the scale of strong interactions. Backed by model simulations, the resulting field is expected to be spatially modulated, deviating significantly from the commonly considered uniform profile. In this work, we present the next step to...
Transport coefficients, such as viscosity, can be calculated theoretically in weakly coupled quantum field theory, and present interesting information about hydrodynamic models of heavy-ion collisions. We present the results for shear viscosity calculations at leading-log in QCD in a regime of high baryon density, where the chemical potentials are greater than the temperature, which is a very...
We study the two-flavour non-local Nambu\textemdash Jona-Lasinio (NJL) model in the presence of a magnetic field and explore the chiral crossover in presence of a non-local form of the 't Hooft determinant term [1]. Its coupling is governed by a dimensionless parameter $c$. This term is responsible for the explicit breaking of $U(1)_A$ symmetry. We have attempted a systematic analysis of the...
We present the properties of open heavy mesons in hot mesonic matter based on a self-consistent theoretical approach that takes into account chiral and heavy-quark spin-flavour symmetries. The heavy-light meson-meson unitarized scattering amplitudes in coupled channels incorporate thermal corrections as well as the dressing of the heavy mesons with the self-energies [1, 2]. As a result, the...
I will describe recent advances in the study of dense quark matter, expected to be present inside the cores of massive neutron stars. I will concentrate on two somewhat differing topics: first, on perturbative studies of the bulk thermodynamic properties of unpaired quark matter, and second, on the application of these results to the model-independent determination of the neutron-star-matter...
Lattice simulations of non-zero density QCD introduce the so-called sign problem, which invalidates importance sampling methods. We use the Complex Langevin equation (CLE) to circumvent the sign problem. Recent results regarding the phase diagram and thermodynamics of QCD using Complex Langevin simulations will be reviewed. Theoretical developments about 'boundary terms' are also discussed: in...
Cold and dense matter can be explored in a systematic way both in the high-density (perturbative
QCD) and low-density (Chiral EFT) regime. However, the path connecting them is yet to be discov-
ered. As a result, these descriptions are usually extrapolated into the intermediate density regime
and then connected at some transition point. In this work I will present a model that has...
We present results on the phase diagram of Quantum Chromodynamics (QCD) with two light quark flavours at finite chemical potential from first principle lattice simulations. To circumvent the sign problem we use the complex Langevin method. The pion mass is of approximately 480 MeV. We report on the pressure, energy and entropy equations of state. A particular emphasis is put on the “cold”...
The possible existence of hybrid stars is studied using several multi-quark interaction channels. The hadronic phase consists of an EOS with presently accepted nuclear matter properties and the quark model constrained by the vacuum properties of several light mesons. The dependence of several NS properties on the different quark interactions is analyzed. We show that the present constraints...
The gauge/gravity duality, combined with information from lattice QCD, nuclear theory, and perturbative QCD, can be used to constrain the equation of state of hot and dense QCD. I discuss an approach based on the V-QCD model, which predicts a strongly first order nuclear to quark matter phase transition with a critical endpoint. By using this model in state-of-the-art simulations of neutron...
By identifying {\em massive} renormalization group (RG) properties within the hard thermal loop (HTL)
formalism, we resum to all orders $\alpha_S^p, p\ge 3$ the leading and next-to-leading logarithmic
soft mode $m_E\sim \alpha_S^{1/2} \mu_B$ contributions to the cold and dense QCD pressure
at high baryon chemical potential $\mu_B$.
We obtain noticeably reduced residual scale dependence...
We study the impact of asymmetric fermionic and bosonic dark matter on neutron star properties,
including tidal deformability, maximum masses, radii, etc. The conditions at which dark matter
particles tend to condensate in the core of the star or create an extended halo are presented. We
show that dark matter condensed in a core leads to a decrease of the total gravitational mass
and tidal...
At extremely high densities, QCD predicts the possible liberation of quark degrees of freedom and the formation of quark matter. The cores of neutron stars (NS) may accommodate such high-density matter. Whether the quark matter exists inside NSs is still an open question. If the quark matter exists, then there should be the imprint of the hadron-to-quark phase transition in the equation of...
We outline the role that an early deconfinement phase transition from normal nuclear matter to a color superconducting quark-gluon plasma phase plays for the phenomenology of supernova explosions and binary neutron star mergers. To this end we extend the compact star equation of state (EoS) from vanishing to moderately high temperatures that become accessible in the CBM experiment at FAIR. We...
The holographic method is one of the only ways of getting analytic insight into most strongly coupled systems. When numerical methods are not available, it is even the best technique we know of to tackle these problems. In particular, lattice QCD is unable to provide results at finite baryon density, which is why a lot of effort is put into the study of holographic QCD at high density....
Using the potential non-relativistic quantum chromodynamics (pNRQCD) framework we derive a Lindblad equation for the evolution of the heavy-quarkonium reduced density matrix that is accurate to next-to-leading order (NLO) in the ratio of the binding energy of the state and the temperature. The resulting NLO Lindblad equation can be used to more reliably describe heavy-quarkonium evolution in...
I discuss three topics in QCD at nonzero temperature and density. First, how confingurations with fractional topological charge $1/N$ in a $SU(N)$ gauge theory may contribute at low temperature. Second, how the Polyakov loop, which appears to be an artifact of Euclidean space-time, can be naturally introduced in the Hamiltonian form, by introducing new states with test charges. Lastly, I...
Suppression of open heavy flavors and quarkonia in heavy-ion collisions is among the most informative probes of the quark-gluon plasma. Interpreting the full wealth of data obtained from the collision events requires a precise understanding of the evolution of heavy quarks and quarkonia as they propagate through the nearly thermal and strongly coupled plasma. In particular, a systematic...
We study jet momentum broadening in heavy-ion collisions at anisotropic initial stages with focus on the jet quenching parameter $\hat q$, which we extract using effective kinetic theory. We obtain its non-equilibrium properties during the bottom-up thermalization scenario in a Bjorken-expanding plasma with non-thermal anisotropic initial conditions.
By studying the time-dependence of the...
I will discuss the potential connection between the entanglement entropy of the initial state and thermodynamic entropy of the final state in relativistic particle collisions, from proton-proton to heavy ion collisions. I will show that simple fragmentation models that ignore quantum mechanical effects break down in describing particle production and that evidence for the non-universality of...
According to the Color Glass Condensate effective theory, the early stages of heavy ion collisions
are described by a quasi-classical state called Glasma, whose dynamics are governed by the Yang-
Mills (YM) equations. Extending prior work [1], we solve the YM equations analytically in the
weak-field limit, which reduces the field strength tensor components to three-dimensional inte-
grals....
Equilibration of quark-gluon plasma in heavy-ion collisions
Not scheduled
25m
Oral presentation Session
Speaker
Dr Xiaojian Du (Bielefeld University)
Description
Non-equilibrium systems are omnipresent in nature. QCD plasma out of equilibrium and its equilibration are of particular interest given that the relativistic heavy-ion collisions (HICs) produce the non-equilibrium quark-gluon...
We revisit the picture of jets propagating in the quark-gluon plasma. In addition to vacuum radiation, related to the high initial virtuality of a jet, jet particles scatter on the medium constituents resulting in induced emissions. Analytical approaches to resumming these interactions have traditionally dealt separately with multiple, soft [1,2], or rare, hard scatterings [3,4]. A full...
Heavy quarks are efficient probes of different physics aspects related to heavy-ion collisions (HIC), as they experience the full evolution of the system. Quarkonia notably provide a direct probe of the deconfinement of nuclear matter. Recently, the production of J/$\psi$ via (re)generation within the quark-gluon plasma (QGP) or at the phase boundary has been identified as an important...
A system of gluon fields generated at the earliest phase of relativistic heavy-ion
collisions can be described in terms of classical fields. Numerical simulations show that the sys-
tem is unstable but a character of the instability is not well understood. With the intention to
systematically study the problem, we analyze a stability of classical chromomagnetic and chromo-
electric fields...
The free energy density of ${\cal N}=4$ supersymmetric Yang-Mills theory in four space-time
dimensions is derived through second order in the 't Hooft coupling $\lambda$
at finite temperature using effective-field theory methods. The contributions to the free energy
density at this order come from the hard scale $T$ and the soft scale $\sqrt{\lambda} T$.
The effects of the scale $T$ are...
In this talk we demonstrate that the early stages of the bottom-up thermalization scenario [1] are well described by the adiabatic hydrodynamization framework. All of the qualitative features exhibited in QCD effective kinetic theory (EKT) simulations at weak coupling [2] are captured by the emergence of an effective low-energy instantaneous ground state for the 1-particle gluon distribution...
We study anomalous transport phenomena with lattice QCD simulations using improved staggered quarks. In particular, we calculate the conductivities both in the free case and in the interacting case, analysing the dependence of these coefficients with several parameters, such as the temperature and the quark mass.
Gribov quantization is a method to improve the infrared dynamics of Yang-Mills theory. We study the thermodynamics and transport properties of a plasma consisting of gluons whose propagator is improved by the Gribov prescription. We first construct the thermodynamics of Gribov plasma using the gauge-invariant Gribov dispersion relation for interacting gluons. When the Gribov parameter in the...
The existence of quark matter inside the cores of massive neutron stars can be probed by modern astrophysical observations. We model these hybrid stars using an (axial)vector meson extended quark-meson model to describe their quark cores, together with various hadronic models. We show that crossover phase transitions between the hadronic and quark phases can naturally create equations of state...
As the strength of the magnetic field ($B$) becomes weak, novel phenomena,
similar to the Hall effect in condensed matter physics
emerges both in charge and heat transport in a thermal
QCD medium with a finite quark chemical potential ($\mu$).
So we have calculated the transport coefficients
in a kinetic theory within a quasiparticle framework,
wherein we compute the effective mass...
It is found from viscous hydrodynamics that the QGP created in ultra relativistic heavy-ion collisions has different longitudinal and transverse pressures at early times. This occurs due to the large momentum space anisotropy in the p_T-p_L plane. This momentum space anisotropy can cause plasma instabilities that are largely responsible for the thermalization and isotropization of the system....
We study the nonperturbative aspects of nonconformal 2+1D Yang-Mills like worldvolume theories on both the isotropic and anisotropic non-supersymmetric D2 brane solution of type II supergravity. Because of broken conformality, the theories for both the cases are found to have running coupling similar to the real world QCD theories. In this context, some salient QCD-like confining properties,...
We present the extraction of the temperature by analyzing the charged particle transverse momentum spectra in lead-lead (Pb-Pb) and proton-proton (${\bf pp}$) collisions at LHC energies from the ALICE Collaboration using the Color String Percolation Model (CSPM) [1]. From the measured energy density ${\varepsilon}$ and the temperature T the dimensionless quantity ${ \varepsilon/}T^{4}$ is ...
The propagation of heavy quarks in the thermal medium closely resembles a Brownian motion characterized by the transport coefficients. In the leading order expansion of inverse mass, these transport coefficients, in particular momentum diffusion, are obtained from the correlators of chromo-electric (E) and chromo-magnetic (B) fields. We investigate longitudinal and transverse diffusion...
We study the impact of asymmetric fermionic and bosonic dark matter on neutron star properties, including tidal deformability, maximum masses, radii, etc. The conditions at which dark matter particles tend to condensate in the core of the star or create an extended halo are presented. We show that dark matter condensed in a core leads to a decrease of the total gravitational mass and tidal...
Non-equilibrium systems are omnipresent in nature. QCD plasma out of equilibrium and its equilibration are of particular interest given that the relativistic heavy-ion collisions (HICs) produce the non-equilibrium quark-gluon plasma (QGP) which eventually emerges to thermal hydrodynamic states. We investigate the kinetic and chemical equilibration of weakly coupled QCD plasma at finite density...
The phase structure of baryonic matter is investigated with focus on the role of fluctuations beyond the mean-field approximation. The prototype test case studied is the chiral nucleon-meson model, with added comments on the chiral quark-meson model. Applications to nuclear matter include the liquid-gas phase transition. Extensions to high baryon densities are performed for both nuclear and...
We propose and apply a new parameterization of the modified chiral effective model to study rotating neutron stars with hyperon core in the framework of the relativistic mean-field theory. The inclusion of the mesonic cross couplings in the model has improved the density content of the symmetry energy slope parameters, which are in agreement with the findings from recent terrestrial...
We demonstrate high prediction accuracy of three important properties that determine the initial geometry of the heavy-ion collision (HIC) experiments by using supervised Machine Learning(ML) methods. These properties are the impact parameter, the eccentricity and the participant eccentricity. Though ML techniques have been used previously to determine the impact parameter of these collisions,...
Using the hard-thermal-loop (HTL) resummation in real-time formalism, we study the next-to-leading order (NLO) quark self-energy and corresponding NLO dispersion laws. In NLO, we have replaced all the propagators and vertices with the HTL effective ones in the usual quark self-energy diagram. Additionally, a four-point vertex diagram also contributes to the quark NLO self-energy. We calculate...
In this talk, we discuss new symmetries of the Cardy-Rabinovici model and their applications. The Cardy-Rabinovici model is the 4d $U (1)$ gauge theory with electric and magnetic matters, and it is a good playground for studying the dynamics of 4d gauge theories. Although this model is not invariant under the $SL(2,\mathbb{Z})$ electromagnetic transformations strictly, we can realize these...
We study temperature fluctuations in the initial stages of the relativistic heavy-ion collision using a multiphase transport model. We consider the plasma in the initial stages after the collision before it has a chance to equilibrate. We have considered Au + Au collision with a varying center of mass energy. We use the non-equilibrium Tsallis statistics to find the entropic index in the...
Finding order parameters for the detection of critical phenomena and self-similar behavior in and out of equilibrium is a challenging endeavour in non-Abelian gauge theories. Tailored to detect topological structures in noisy data and accompanied by stability and limit theorems, persistent homology allows for the construction of sensible and sensitive observables. Based on state-of-the-art...
In the presence of an external uniform magnetic field $B$, we show that new axial and vector decay constants appear for pions. A general expression for the weak decay $\pi^- \rightarrow l^- \bar{\nu}_l$ is also obtained. We calculate these decay constants within the Nambu-Jona--Lasinio (NJL) model, obtaining an enhancement of the total decay rate up to $\sim 10^3$ for $\mathrm{eB}$ = 1...
I will discuss the potential connection between the entanglement entropy of the initial state and thermodynamic entropy of the final state in relativistic particle collisions, from proton-proton to heavy ion collisions. I will show that simple fragmentation models that ignore quantum mechanical effects break down in describing particle production and that evidence for the non-universality of...
I will review recent results on lattice QCD at finite temperature and density, with special emphasis on the QCD equation of state, phase transition line and fluctuations of conserved charges.
I will present a summary of results on parity invariant quantum electrodynamics in three Euclidean dimensions using lattice regularization. The results will show scale invariance independent of the number of massless fermions. Results for monopole scaling dimensions and their relevance will also be discussed.
Skyrme model is among the simplest extensions of chiral effective theory including anomaly. Within such framework we investigate how an external magnetic field deforms a Skyrmion while preserving its topological winding. A crystal constituted by multiple magnetically deformed Skyrmions provides us insights of the ground state of nuclear matter in strong magnetic field. We manifest such Skyrme...
The aim of this project is to compute the strong sphaleron rate (the diffusion constant for the Chern-Simons topological number for quantum chromodynamics) on 4D lattices in a range of temperatures between 500 MeV and 3 GeV. This rate is important to understand the equilibration between axial quarks through the anomaly equations. Although this quantity has been previously computed in real-time...
More than 20 years ago, Glendenning et al. (1995) proposed the existence of stable white dwarfs with a core of strange quark matter. More recently, by studying radial modes, Alford et al. (2017) concluded that those objects are unstable. We investigate again the stability of these objects by looking at their radial oscillations, and we assume that there is no phase transition between hadronic...
A system of gluon fields generated at the earliest phase of relativistic heavy-ion
collisions can be described in terms of classical fields. Numerical simulations show that the system is unstable but a character of the instability is not well understood. With the intention to systematically study the problem, we analyze a stability of classical chromomagnetic and chromoelectric fields which...
Cold and dense matter can be explored in a systematic way both in the high-density (perturbative QCD) and low-density (Chiral EFT) regime. However, the path connecting them is yet to be discovered. As a result, these descriptions are usually extrapolated into the intermediate density regime and then connected at some transition point. In this work I will present a model that has features of...
We generalize a complex heavy-quark potential model from an isotropic QCD plasma to an anisotropic one by replacing the Debye mass $m_D$ with an anisotropic screening mass depending on the quark pair alignment with respect to the direction of anisotropy.
Such an angle-dependent mass is determined by matching the perturbative contributions in the potential model to the exact result obtained in...
We study the thermal transitions of dense two colour QCD with two flavours of Wilson fermions at a fixed chemical potential $\mu=443$ MeV on a coarse isotropic lattice $a=0.18$ fm. The results on a larger lattice volume ($N_s=24$) are compared with earlier results with the same lattice spacing but a smaller lattice volume ($N_s=16$). Only small finite volume effects are found.
We also...
We study thermalization of gluons with momentum $p$ characterized by $Q$ in spatially homomgeneous systems. In initially under-populated systems in which the equilibrium temperature $T\ll Q$, soft gluons are found to be rapidly generated via radiation to fill a classical thermal distribution $\propto T^*/p$ with $T^*\gg T$. Thermal equilibrium is established only after $T^*$ approaches to $T$...
Quantum Chromodynamics, the theory of strong interactions, predicts the existence, under extreme conditions, of a deconfined state of matter known as the quark-gluon plasma (QGP). We have strong evidence that such an extreme state is produced in relativistic heavy-ion collision experiments, such as RHIC and the LHC. A daring question is what is the smallest possible QGP size, one that can be...
We study the thermoelectric response of a thermal medium of deconfined quarks and gluons in the framework of relativistic kinetic theory. The response of the medium is quantified by the Seebeck and Nernst coefficients which relate the mutually longitudinal and transverse components, respectively, of the induced electric field and the temperature gradient. To obtain the above coefficients, we...
We compare the behavior of zero-modes of the overlap Dirac operator measured on the finite temperature 2+1 flavor lattice QCD configurations, generated with domain wall fermion discreitzation, to the local Polyakov Loop in the temperature range 1.1-1.2T_c, T_c being the pseudo-critical temperature. We show how the position of the zero-modes are anti-correlated to the local value of the Polyakov Loop.
The introduction of electric and magnetic fields in the QCD vacuum generates topological sectors with a non-zero topological charge. For weak fields, there is a linear response for the topological charge. We study this linear response which can be interpreted as the axion-photon coupling. In this work we use lattice simulations with improved staggered quarks including background electric and...
