The properties of QCD with massless quarks, particularly the chiral phase transition, have important implications for our understanding of QCD at the physical point. Once the number of massless fermions exceeds a critical value, $N_f^*$โ, QCD enters the conformal window and becomes chirally symmetric already in the vacuum. Determining $N_f^*$โ has long been a challenge in lattice QCD, as...
A quantitative analysis of the universal aspects of QCD phase transition is required to achieve good control of the continuum as well as, infinite volume and chiral limits. In this talk, we will present a careful analysis of the latter two limits, taken at fixed values of lattice cut-off in the framework of (2+1)-flavor QCD. Although this does not yet allow to determine the universality class...
Phase boundary in the lower left corner of Columbia plot has been studied extensively. We have been tackling this problem using Mรถbius domain wall fermions of JLQCD type. With an extended analysis as well as the increased statistic around the physical $ud$ quark mass for the three degenerate quarks, we will make conclusion for the $N_t=12$ lattice. With that and glancing the results so far...
We report recent results on the finite-temperature chiral phase transition in (2+1)-flavor QCD with physical quark masses, using the Mรถbius domain wall fermion (MDWF) action to preserve chiral symmetry to a high precision. Our simulations cover a temperature range from 140 to 250 MeV for two lattice spacings, corresponding to temporal extents of $N_t = 12$ and $16$, with aspect ratios...
Lattice simulations based on importance sampling suffer from the infamous sign problem when applied to certain physical systems of interest, such as QCD at finite baryon density or real-time quantum field theories. A possible way out is provided by the complex Langevin approach, which is based on a stochastic evolution of complexified degrees of freedom in an auxiliary time direction. However,...
Computations at imaginary values of chemical potential is one of the most popular ways to tackle the sign problem in lattice simulations.
For this reason, it is important to study different ways to perform the analytic continuation to the real axis.
In the context of the Bielefeld-Parma collaboration, we have been generating data which fed our multi-point Padรฉ analysis of the QCD phase...
Mapping the QCD phase structure at finite baryon density remains a challenging problem because direct simulations are hindered by the sign problem. By analyzing results at vanishing and purely imaginary chemical potentials, we identified strangeness susceptibility, in the case of strangeness neutrality, as a proxy for the chiral transition. We exploit this observation to investigate the QCD...
We build an EFT which accurately captures low energy physics of the chiral sector of QCD. When fitted to properties of pions at finite temperature obtained from lattice simulations of 2+1 flavour QCD, it accurately reproduces the crossover temperature seen in the simulations. Its predictions for other quantities are shown. The EFT can then be used for analytic continuation to real time. An...
We present our latest results on charmonium states $J/\psi(1S)$, $\psi(2S)$, $\eta _c(1S)$, $\eta _c(2S)$, $\chi _{c0}(1P)$ and $\chi _{c1}(1P)$ above the pseudo-critical temperature, using extended operators [1] on $N_x=64$, $N_\tau =16-32$ HISQ lattices using Wilson Clover fermions.
The charmonium states at zero temperature are well described by the heavy quark anti-quark potential. At...
In this work we calculate the non-perturbative potential between a heavy quark and an anti-quark pair in a QCD plasma at finite temperature. Extracting the leading order static potential $V_s(r)$ from the temporal Wilson line correlators we then calculate the spin dependent component $V_{ss}(r)$ at $\mathcal{O}(1/M^2)$, using color-magnetic field insertions. The computations have been...
We investigate how quarkonium states are affected by a medium with non-zero isospin chemical potential at near zero temperature. We obtain quarkonium correlators from heavy quark propagators which are calculated via lattice Non-Relativistic QCD (NRQCD) on the gauge field ensembles simulated with non-zero isospin chemical potential. Here, the gauge field ensemble with $\mu_I a = 0.000, 0.048,...
The modification of heavy-quark interactions in hot and dense QCD matter plays a central role in understanding the fate of quarkonium in heavy-ion collisions. While lattice QCD studies at zero chemical potential have established the temperature dependence of the static quarkโantiquark potential and its spectral properties, the finite baryon density regime remains largely unexplored. In this...
We study spectral reconstruction techniques to obtain the electric conductivity coefficient at non-zero external magnetic fields for Wilson fermions in quenched QCD from the euclidean correlator. Spectral reconstruction is a well studied numerically ill-posed problem which arises due to the relation of the euclidean correlator to the spectral function via an inhomogenous Fredholm equation of...
We study some of the outstanding non-perturbative properties of QCD at finite temperature $T$ due to the magnetic gluons whose momenta are $|\vec{p}|\leq g^2T/\pi$, where $g$ is strong coupling strength. By performing lattice computations of the spatial Wilson line correlators for a wide range of temperatures from $160$-$1000$ MeV on different lattice spacings corresponding to $N_\tau=8, 12,...
We calculate spatial string tension in 2+1 flavour QCD in (3,1)
dimensions within temperature range of [166MeV, 1000MeV] using spatial
Wilson Loops with HYP smearing. We used Highly Improved Staggered Quark
action for
fermions and tree level Symanzik improved gauge action for gluons at two
lattice spacings corresponding to temporal extent $N_{\tau}=8,10$. We
then compare our results...
Novel theoretical and computational strategies have opened the possibility of exploring QCD thermodynamics at the non-perturbative level at unprecedented temperatures, reaching from the GeV scale up to the electroweak scale.
A number of observable quantities are now being investigated in this regime.
Key ones are the hadronic screening masses, which encode the correlation length of the...
The $U(1)_A$ symmetry of the massless QCD Lagrangian is broken in the quantised theory but may be effectively restored at some finite temperature with important consequences on the order of the chiral transition and the QCD phase diagram in the chiral limit. It has been argued in the literature that one way to probe the effective restoration of $U(1)_A$ is to check for the degeneracy of...
In this work, we calculate the eigenvalues of the probe (overlap) Dirac operator on thermal gauge ensembles of 2+1 flavor QCD generated using domain wall fermions as well as pure SU(3) gauge theory on the lattice. Focusing on the infrared part of the eigenspectrum that lies within the non-perturbative magnetic scale, we propose suitable observables that allow us to categorize different regions...
The topological susceptibility is one of the quantities that has a large discretization error, and the error can be sensitive to the choice of fermion action. We report on our results from physical point simulations with 2+1 flavor Moebius domain wall fermion at finite temperature. The temporal lattice size is Nt=12 and 16, and the temperature range is around 140 MeV to 250 MeV. We also...
The nature of the finite temperature phase transition of QCD depends on the particle density and the mass of the dynamical quarks. It is known that the transition is first order in the region of zero density and heavy quark mass, and also first order in the region of light quark mass when the number of flavors is large. The intermediate region is the crossover region, and numerical simulations...
Strong magnetic fields can profoundly affect the equilibrium properties, characterized by the equation of state and bulk thermodynamics of strongly interacting matter. Although such fields are expected in off-central heavy-ion collisions, directly measuring their experimental imprints remains extremely challenging. To address this, in this talk we propose the baryon-electric charge...
We investigate the static-quark entropy in QCD in the presence of external magnetic fields, using its temperature peak as a pseudocritical deconfinement indicator. Our calculations employ HISQ fermions with a tree-level improved Symanzik gauge action at physical quark masses, on lattices with temporal extents $N_\tau = 8, 12$ and fixed aspect ratio $N_\sigma/N_\tau = 4$. A two-dimensional $(T,...
The QCD Anderson transition is believed to be connected to both, confinement and chiral symmetry breaking. We investigate the latter relation by studying the low-lying eigenmodes of the overlap operator in the background of gauge configurations with 2+1+1 quark flavors of twisted-mass Wilson fermions. The mobility edge, below which eigenmodes are localized, is estimated by the inflection point...
We present an extended version of the k-Shape method, originally developed for time-series clustering, and apply it to lattice simulations of the finite-temperature and finite-density (1+1)-dimensional GrossโNeveu model. The method has been generalized from real to complex scalar fields and from one-dimensional to multidimensional configurations, allowing a detailed analysis of spatially...
Drawing upon well established zero-temperature techniques, we present, for the first time, insight into the fate of the $1^{-+}$ exotic charmonium state at finite temperature using anisotropic FASTSUM ensembles. Specifically, we use distillation with a wide operator basis which has been extensively used at zero-temperature by the Hadron Spectrum Collaboration to study the charmonium spectrum....
We demonstrate the chaoticity inherent in SU(2) gauge theory consisting of soft momentum modes both in and out-of-thermal equilibrium conditions using lattice techniques. The non-equilibrium state has been realized starting from an over-occupied initial condition for low momentum soft gluons whereas the thermal state comprises of strongly interacting soft gluons at temperatures where these are...
Quark-gluon plasma created in heavy-ion collision experiments is subjected to huge acceleration which might modify QCD properties. The toy model which allows to study the influence of
acceleration on a strongly interacting system is QCD in the Rindler space. In addition the Rindler space allows to consider QCD properties close to the event horizon of a black hole.
In this report the first...
Using first-principle numerical simulations, we find a new spatially inhomogeneous phase in rotating gluon plasma. This mixed phase simultaneously contains regions of both confining and deconfining states in thermal equilibrium. The location of the spatial transition between the two phases is determined by the local critical temperature. We measure the local critical temperature as a function...
