Dileptons are considered to be an important observable, in the context of studying the characteristics of the deconfined phase of quark gluon plasma (QGP). Historically, the dilepton production rates (DPR) from the QGP have been studied using two different approaches. In the quantum field theory (QFT) approach, the DPR is expressed in terms of the thermal expectation value of the...
We study the bulk viscosity of moderately hot and dense, neutrino-transparent colour superconducting quark matter arising from weak-interaction-driven direct URCA processes. The quark matter is modeled using the Nambu-Jona-Lasinio model extended to include both vector interactions and the 't Hooft determinant term. The superconducting phase is described by using the two-flavour red-green...
We present a lattice QCD study of light pseudoscalar meson masses and decay constants in strong background magnetic fields, using three different lattice sizes. Our simulations employ (2+1)-flavor ensembles using the highly improved staggered quark (HISQ) action with physical quark masses and three values of the lattice spacing ($a \approx$ 0.067, 0.084, 0.112 fm) to enable a controlled...
We review recent progress towards the understanding of the QCD phase diagram using tools based on effective theories, Ward Identities (WI) and resonances at finite temperature and chemical potentials.
Various relevant observables such as scalar and topological susceptibilities can be obtained within this framework and are consistent with recent lattice analyses. In particular, we show...
In this talk I will discuss the three-flavor quark-meson model including color superconductivity, with emphasis on the 2SC and CFL phases. We extend the quark-meson model to the quark meson diquark model. This is a renormalizable low energy effective model that describes the superconductive phases of QCD. We calculate the thermodynamic potential including quark loops. We map out the phase...
We explore the role of color superconductivity in quarkyonic matter under the conditions of electric and charge neutrality at β-equilibrium, as relevant for neutron stars. By explicitly incorporating color-superconducting pairing gap into the phenomenological model of a crossover transition from hadron to quark matter, we extend the known quarkyonic framework suggested by McLerran and Reddy to...
We present the in-medium mass modification of $D$ ($D^+$, $D^0$) and $\bar D$ ($D^-$, $\bar {D^0}$) mesons when immersed in isospin asymmetric $\Delta$ resonance matter by using the chiral SU(3) hadronic model extended to the SU(4) sector.
The interactions of $D$ and $\bar D$ mesons with decuplet baryons ($\Delta^{++,+,0,-}$) are explicitly taken into account in the dispersion relations in...
In this talk I will present a new method to study the QCD phase diagram at finite baryon chemical potential, using hadronic correlators. Specifically, the approach exploits the degeneracy between the vector and axial vector channels upon chiral symmetry restoration. The temperature at which this degeneracy occurs shifts as $\mu_B$ is increased, allowing us to follow the change of $T_{c}$ along...
Dense QCD matter can feature a moat regime, where the static energy of mesons is minimal at nonzero momentum. We elucidate various features of this regime in this work. To capture the main effects, we use a two-flavor quark-meson model and put forward an efficient renormalization scheme to account for the nontrivial momentum dependence of meson self-energies in the moat regime.
We show that...
We analyze the finite-temperature equation of state (EOS) within the framework of an effective Lagrangian, where a dilaton field encodes the breaking of scale invariance in QCD. The present work extends a previous study in the pure gauge SU (3)c sector [1], in which the dynamics of the gluon condensate are described through a dilaton Lagrangian. Below the critical temperature, the condensate...
We present an improved ansatz for the self-energy of confined quarks within a density functional formalism in order to investigate the thermodynamics of dense matter, particularly, the speed of sound and baryon fluctuations, including studying their approach toward the conformal limit. The formulation offers insight into how characteristic scales inherent to a theory lead to mimicking...
At present, our understanding of the non-equilibrium aspects of a relativistic spin fluid is derived from the study of Wigner function coupled with the semiclassical expansion. In our work, we present an exact computation (up to quantum loop corrections) of the Wigner functions for quarks in a field of oscillating pion condensate. The oscillating pion condensate enters the equation of motion...
Fragmentation functions are fundamental components of the factorization approach which is used to calculate the production cross sections of heavy-flavor hadrons within QCD. Due to their non-perturbative nature, they cannot be computed a priori and are typically extracted from measurements in clean environments such as electron-positron (e$^+$e$^-$) or electron-proton (e$^-$p) collisions....
The experimental observation of the spin polarisation of the outgoing hadrons in non-central heavy ion collisions implies the existence of a strongly vortical QGP medium with finite spin density. We consider the effect of finite spin density on the QCD phase diagram using the Linear Sigma model coupled to quarks (LSMq). In our approach, we introduce the finite spin density via a quark spin...
We study the magnetic properties of the Hadron Resonance Gas (HRG) (which is created in ultra-relativistic heavy-ion collisions or studied on the lattice) in the presence of a constant magnetic field. Instead of the simplified approach$^{1,2}$ of taking the gyromagnetic ratio of a hadron as $g=2|Q|$, we consider the physical value of $g$ as measured in experiments or estimated theoretically....
We investigate the rotational Brownian motion of heavy quarks in a QCD medium and present predictions for the polarization of open heavy-flavor hadrons. Specifically, we derive expressions for vector and tensor polarization, which correspond to baryon spin polarization and meson spin alignment, respectively. Furthermore, we suggest that the transverse momentum dependence of heavy quark...
We compute the pressure, chiral condensate and strange quark number susceptibility from first principles within perturbative QCD at finite temperature and very high magnetic fields up to two-loop and physical quark masses. We also discuss cold and dense quark matter in the presence of a very strong magnetic field using perturbative QCD at finite density. The effectively negligible contribution...
A recently formulated extension of perfect spin hydrodynamics, which includes second-order corrections in the spin polarization tensor to the energy-momentum tensor and baryon current, is studied in the case of a one-dimensional boost-invariant expansion. The presence of second-order corrections introduces feedback from spin dynamics on the hydrodynamic background, constraining possible spin...
The extraordinary densities achieved in the cores of neutron stars make them ideal astrophysical laboratories for investigating hypernuclear matter. Recent multi-messenger observations impose stringent constraints on the neutron star equation of state, allowing for tests of models that incorporate exotic components such as hyperons. For example, precise measurements of neutron star masses—such...
We study neutron stars (NSs) admixed with self-interacting bosonic dark matter (DM), motivated by recent observational data from NICER and LIGO/Virgo. In this framework, sub-GeV bosonic DM can accumulate as a dense core or form an extended halo around the NS, significantly affecting its mass, radius, and tidal deformability. By varying the DM particle mass, self-coupling strength, and its...
The encoded nuclear structures related to flow fluctuations can be investigated at a fixed impact parameter in ultra-relativistic ion collisions through the concept of factorization breaking. This phenomenon is explored by analyzing momentum-dependent correlations among flow harmonics across distinct kinematic bins, specifically in terms of pseudorapidity ($\eta$)[1] or transverse momentum...
We employ lattice simulations to search for the critical point of quantum chromodynamics (QCD). We search for the onset of a first order QCD transition on the phase diagram by following contours of constant observables (e.g. entropy density) from imaginary to real chemical potentials under conditions of strangeness neutrality. We scan the phase diagram and investigate whether these contours...
Rotation is known to restore chiral symmetry at high angular velocities, but it is also expected that rotation can induce an axial-vector condensate. This condensate, often overlooked, can significantly alter the behavior of the chiral condensate, potentially enhancing it under rapid rotation. To investigate this interplay, we compute the phase diagram of the chiral and axial vector...
First-principle lattice QCD studies of the Chiral Magnetic Effect (CME) have so far been mostly carried out in a thermal equilibrium state with background magnetic field and an artificial "chiral chemical potential". In this case, Bloch theorem prohibits any nonvanishing conserved currents in equilibrium, and the CME current vanishes identically.
In this talk, I introduce a novel formalism...
The predictions of QCD at temperatures ranging from 1 GeV up to 160 GeV have recently become accessible from first-principles, non-perturbative lattice simulations owing to a novel computational strategy. Among the quantities that are being investigated in the ongoing program, hadronic screening masses - i.e. inverse correlation lengths - offer crucial insight into the properties of the QCD...
Stochastic hydrodynamics provides a dynamical framework for the evolution of fluctuations in heavy-ion collisions. Due to the small volume of the system, thermal fluctuations can become sizeable and probe the equation of state of the system, being particularly sensitive to a possible QCD critical endpoint.
Our present numerical setup can simulate stochastic non-relativistic hydrodynamics in a...
In this talk, I will present our latest research building upon the findings of PLB 850 (2024) 138533, which demonstrated that the entropy current can be derived from first principles using the quantum statistical method, bypassing the need for assumed traditional local thermodynamic forms. Our study uncovers that the local thermodynamic relations, which have been conventionally used as...
Heavy quarkonium serves as an excellent probe to study the properties of the Quark-Gluon Plasma (QGP). The physics of quarkonium created in heavy-ion collisions is intrinsically connected to the correlation functions of adjoint chromoelectric fields in quantum chromodynamics. Such correlation functions are vital in determining transport coefficients that govern the evolution of heavy...
We study the impact of asymmetric fermionic and bosonic dark matter on neutron star properties, including tidal deformability, maximum masses, radii, thermal evolution, moment of inertia, etc. The conditions under which dark matter particles tend to condense 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...
We investigate the influence of nuclear structure on transverse spherocity ($S_0$) distributions in $^{238}U+^{238}U$ collisions at $\sqrt{S_{NN}}=193$ GeV. The initial spatial anisotropy of colliding nuclei is expected to imprint distinct signatures on final-state event topology. Hydrodynamic evolution translates these initial geometric anisotropies into momentum-space correlation via...
By consideration of the Compact object HESS J1731-347 as a hybrid twin compact star, i.e., a more compact star than its hadronic twin of the same mass, its stellar properties are derived. Besides showing that the properties of compact stars in this work are in good agreement with state-of-the-art constraints both from measurements carried out in laboratory experiments as well as by...
Major progress has been made in recent years toward computing the four-loop perturbative pressure of cold and dense quark matter (QM) [1,2], a key ingredient in constraining the equation of state of neutron-star matter. What remains to be computed is the contribution from hard-momentum gluons in dense QCD, encoded in the sum of 52 four-loop vacuum Feynman diagrams at finite baryon chemical...
Employing a kinetic framework, we calculate all transport coefficients for relativistic dissipative (second-order) hydrodynamics for arbitrary particle masses in the 14-moment approximation. Taking the non-relativistic limit, it is shown that the relativistic theory reduces to the Grad equations computed in the “order-of-magnitude” approach.
While symmetric nuclear matter has been studied in laboratories, neutron star matter is characterized by high asymmetry. Therefore, by examining the strongly interacting matter properties in a wide range of densities and isospin asymmetry we confront two regimes to understand how the enforced electric neutrality and beta equilibrium alter the onset density of quark matter. Particularly, we...
Recent studies suggest that the presence of a peak structure in the sound velocity would be essential for reproducing the observed mass-radius relation of neutron stars. To investigate the existence of the sound velocity peak in baryonic dense matter, the chemical potential dependence of the sound velocity has recently been evaluated via lattice simulations of two-color QCD, rather than...
We propose a hybrid approach, which may help to establish consistency between different formulations of spin hydrodynamics. The perfect fluid is described in the framework of kinetic theory of particles with spin 1/2 following the Fermi-Dirac statistics. The baryon number, energy, linear momentum, the spin part of angular momentum, as well as entropy are conserved, although in the presence of...
Diffusion models are currently one of the leading generative AI approaches for image generation used by e.g. DALL-E and Stable Diffusion. A formulation familiar to physicists uses stochastic differential equations. We review this formulation and relate it to stochastic quantisation in quantum field theory. We demonstrate the approach for scalar and abelian gauge fields in two dimensions and...
In the last years, several exotic states have been observed in the charm sector; such particles cannot be interpreted as baryons or mesons and are thought to be either quark bags or molecular states. To unveil the nature of those states, it is crucial to experimentally constrain the strong force that governs the interaction between the charmed hadrons and other hadrons, e.g. via the...
In this work, we calculate the phase diagram of the (2+1)-dimensional Gross-Neveu-Yukawa (GNY) model under strong magnetic fields at finite temperature and density. Large magnetic fields result in magnetic catalysis, a dimensional reduction of the system and enhancement of the chiral symmetry breaking. Using the functional renormalization group (FRG) in a hydrodynamic approach allows us to...
We use the functional renormalization group in the local potential approximation, with the full effective potential, to investigate the quark meson model for the presence of inhomogenious phases. To this end, we solve the flow equation for the bosonic two point function, to investigate if the two point function shows a negative wave function renormalization or even a zero...
The $\psi(3686)$ is identified as the radial excitation of the $J/\psi$. Based on perturbative QCD, the branching ratio of the $\psi(3686)$ into some final hadron state should be approximately 13\% of the branching ratio of the $J/\psi$ to that same hadron final state. This is called the "13\% rule". However, certain decay channels such as the $\rho\pi$ severely violate this 13\% rule. Using...
We explore the phase diagram of 8 flavor QCD by lattice simulations, using a stout improved staggered fermion action and a tree-level Symanzik improved gauge action. At small masses we observe an intermediate phase between the strong coupling and the weak coupling phases, aligning with results from previous studies. We also investigate the effect of adding an imaginary chemical potential.
We investigate the transport properties of quark matter under conditions of momentum anisotropy using the Polyakov chiral quark mean-field (PCQMF) model. Momentum anisotropy naturally arises in systems out of equilibrium, such as the early stages of relativistic heavy-ion collisions or the interior of compact stars. Understanding the impact of such anisotropy on transport coefficients is...
An understanding of the properties of the quark-gluon plasma (QGP) is important for the interpretation of experimental data on the bulk observables, as well as on jet and heavy-quark attenuation in heavy-ion collisions. However, gaining this knowledge is a challenging task, since it pertains to the non-perturbative regime of QCD, for which only limited information from lattice QCD is currently...
The chiral phase transition in (2+1)-flavor QCD is expected to be of second order, if the breaking of axial anomaly remains sufficiently strong at the chiral phase transition temperature $T_c$ [1]. This observation is supported by the lattice QCD calculations [2]. However, the FRG model calculations suggest that the scaling window may be small [3], within which the universal scaling relations...
The observation of significant Λ hyperon transverse polarization, i.e. the polarization in the direction transverse to the Λ production plane, in inclusive p+p and p+A collisions using unpolarized beams triggered theoretical efforts to describe this effect. Numerous models have been proposed to explain the origin of hyperon polarization. Several models have successfully explained the behavior...
