We compute the spectral densities of $T^{μν}$ and $J^μ$ in high temperature QCD plasmas at small frequency and momentum,\, $ω,k \sim g^4 T$. The leading log Boltzmann equation is reformulated as a Fokker Planck equation with non-trivial boundary conditions, and the resulting partial differential equation is solved numerically in momentum space. The spectral densities of the current, shear, sound, and bulk channels exhibit a smooth transition from free streaming quasi-particles to ideal hydrodynamics. This transition is analyzed with conformal and non-conformal second order hydrodynamics, and a second order diffusion equation. We determine all of the second order transport coefficients which characterize the linear response in the hydrodynamic regime.
We derive an expression for the heavy quark damping rate in hot quark gluon plasma in presence of flow. Here all the bath particles here are out of equilibrium due to the existence of non-zero velocity gradient. The magnetic sector shows similar infrared divergences even after hard thermal loop corrections as one encounters in case of non-viscous plasma. We estimate the first order correction in ($η/s$) for heavy quark damping rate due to the non-zero viscosity of the QCD plasma.
We extend a previous work on the study of heavy charmonia and bottomonia in a deconfined quark-gluon plasma by considering the Bc family of mesons. With the introduction of this bound state of a charm and a beauty quark, we investigate at finite temperature the behavior of the quarkonium, in an energy region between the ψ and the Υ states.
We calculate the bound state properties of $J/ψ$ in a hot and dense QCD plasma using phenomenological potentials augmented by inputs from perturbative QCD. The temperature and density region of study will be relevant in future heavy ion collision experiments at FAIR. We find that the effect of baryon density on the dissociation of $J/ψ$ is small in this regime. However we indicate that if there is a critical end point in the QCD phase diagram then strong density fluctuation will dissociate charmonia near hadronization. The measurement of $J/ψ$ suppression can therefore signify the existence of…
We calculate the free energy of a hot gluon plasma to leading order in hard-thermal-loop perturbation theory. Effects associated with screening, gluon quasiparticles, and Landau damping are resummed to all orders. The ultraviolet divergences generated by the hard-thermal-loop propagator corrections can be cancelled by a temperature-independent counterterm. The deviation of the hard-thermal-loop free energy from lattice QCD results for T > 2 T_c has the correct sign and roughly the correct magnitude to be accounted for by next-to-leading order corrections.
The quantum kinetics of photons is studied directly in real time by implementing the dynamical renormalization group. In contrast to conventional approach, the dynamical renormalization group method consistently includes off-shell (energy non-conserving) effects and accounts for time-dependent collisional kernel. To lowest order we find that in the relaxation time approximation the semihard photon distribution function relaxes with a power law.
We present the derivation of heavy quark energy loss in a viscous QCD plasma using kinetic theory. Shear flow changes both boson and fermion distribution functions which eventually modify heavy quark energy loss. Due to presence of non-zero flow gradient in the medium all the bath particles here are out of equilibrium. In these types of plasmas we show that without plasma screening effects heavy quark energy loss suffers similar type of infrared divergence as one encounters in non-viscous plasma. The screening effects are incorporated consistently through Hard Thermal Loop resummation perturba…
Considering the low-temperature ($T$) and high-baryon-number-density ($n_B$) region of the QCD phase diagram, we present a model for the first-order phase transition between the quark-gluon plasma (QGP) and the recently proposed colour superconducting phase. We study nucleation of a droplet of the superconducting phase within the metastable QGP gas. Numerical results for the activation energy, radius and other physical parameters of the droplets, at various temperatures, densities and gap parameters, are given. We have estimated the latent heat of the phase transition. In the $T-n_B$ plane, we…
We compare two mechanisms for the dissociation of heavy mesons in an infinite quark-gluon plasma: dynamic Debye screening and multiple scattering. Using the uncertainty principle inspired by a Schrodinger-like equation, we find that the criterion a_B\simeq1/μ\simeq 1/(α_{eff}^{1/2}T) with α_{eff}\equivα(N_c+{N_f\over2}) is parametrically true both for the dissociation of fast moving heavy mesons with a size a_B due to dynamic Debye screening as well as for mesons at rest in the medium. In contrast, we find that the criterion for the dissociation of heavy mesons due to uncorrelated multiple sca…
We compute the energy loss of heavy quarkonia in high temperature QCD plasmas and investigate the energy loss effects on quarkonium suppression. Based on the effective vertex derived from the Bethe-Salpeter amplitude for quarkonium, the collisional and radiative energy loss are determined by quarkonium-gluon elastic scattering and the associated gluon-bremsstrahlung, respectively. In the energy regime $E<m_Υ^2/T$ the collisional energy loss is dominant over the radiative one, and the total energy loss increases with the plasma temperature and the initial energy of quarkonium. Our numerical ana…
We investigate possible mass shift and width broadening of J/psi in hot gluonic matter using QCD sum rule. Input values of gluon condensates at finite temperature are extracted from lattice QCD data for the energy density and pressure. Although stability of the moment ratio is achieved only up to T/Tc ~ 1.05, the gluon condensates cause a decrease of the moment ratio, which results in change of spectral properties. Using the Breit-Wigner form for the phenomenological side, we find that mass shift of J/psi just above Tc can reach maximally 200 MeV and width can broaden to dozens of MeV.
Thermal (Th-)QCD properties appear to disagree with lattice (L-)QCD results, which suggests that Th-QCD does not have a valid perturbative expansion. However, we reproduce L-QCD using the first order $α_s$ corrections in Th-QCD.
We consider a transport equation of the Boltzmann-Langevin type for non-Abelian plasmas close to equilibrium to derive the spectral functions of the underlying microscopic fluctuations from the entropy. The correlator of the stochastic source is obtained from the dissipative processes in the plasma. This approach, based on classical transport theory, exploits the well-known link between a linearized collision integral, the entropy and the spectral functions. Applied to the ultra-soft modes of a hot non-Abelian (classical or quantum) plasma, the resulting spectral functions agree with earlier f…
The partonic energy loss has been calculated taking both the hard and soft contributions for all the $2 \to 2$ processes, revealing the importance of the individual channels. Cancellation of the intermediate separation scale has been exhibited. Subtleties related to the identical final state partons have properly been taken into account. The estimated collisional loss is compared with its radiative counter part. We show that there exists a critical energy ($E_c$) below which the collisional loss is more than its radiative counterpart. In addition, we present closed form formulas for both the c…
We estimate here the electrical and Hall conductivity using a quasiparticle approach for quark matter. We use a Boltzmann kinetic approach in presence of external magnetic field. We confront the results of model calculations with Lattice QCD simulations for vanishing magnetic field. In general electrical conductivity decreases with magnetic field. The Hall conductivity on the other hand can show a non monotonic behaviour with magnetic field due to an intricate interplay of behaviour of relaxation time and strength of the magnetic field. We argue for vanishing quark chemical potential Hall cond…
We present results for the evolution of the momentum distribution of a hard parton traversing a brick of quark-gluon plasma, considering both bremsstrahlung and collisional energy loss. The complete leading order transition rates are included. We find a significant modification of the evolving momentum distribution compared to results obtained by employing an approximate implementation of the collisional energy loss that uses the mean energy loss, together with momentum diffusion.
We study the propagation of energy density perturbation in a hot, ideal quark-gluon medium in which quarks and gluons follow the Tsallis-like momentum distributions. We have observed that a non-extensive MIT bag equation of state obtained with the help of the quantum Tsallis-like distributions gives rise to a breaking wave solution of the equation dictating the evolution of energy density perturbation. However, the breaking of waves is delayed when the value of the Tsallis q parameter and the Tsallis temperature T are higher.
The quark-gluon plasma in stellar structure is investigated using the fluid-like QCD approach. The classical energy momentum tensor relevant for high energy and hot plasma having the nature of fluid bulk of gluon sea is calculated within the model. The transition of gluon field from point particle field inside stable hadrons to relativistic fluid field in hot plasma and vice versa is briefly discussed. The results are applied to construct the equation of state using the Tolman--Oppenheimer--Volkoff equation to describe the hot plasma dominated stellar structure.
We discuss the glueball contribution to the equation of state (EoS) of hot gluon matter below and above $T_c$. It is shown that the strong changing of masses of scalar and pseudoscalar glueballs near $T_c$ plays very important role in the thermodynamics of $SU(3)$ gauge theory. In particular, we give the arguments that these glueballs become massless at $T_G\approx 1.1T_c$ and this phenomenon is crucial in understanding of the mystery in the behavior of trace anomaly founded in the lattice calculation.
We present new results on the equation of state and transition line of hot and dense strongly interacting QCD matter, obtained from a bottom-up Einstein-Maxwell-Dilaton holographic model. We considerably expand the previous coverage in baryon densities in this model by implementing new numerical methods to map the holographic black hole solutions onto the QCD phase diagram. We are also able to obtain, for the first time, the first-order phase transition line in a wide region of the phase diagram. Comparisons with the most recent lattice results for the QCD thermodynamics are also presented.
We study how local fluctuations in the initial states of relativistic heavy-ion collisions manifest themselves in the correlations between different orders of harmonic moments of the density profiles, particularly those involving only odd harmonics which purely arise from initial state fluctuations. We find the strengths of those correlations are sensitive to the number of hot and cold spots in the initial states. Hydrodynamic evolution of the fireball translates initial state geometric anisotropies as well as their correlations into final state momentum anisotropies and correlations. We concl…
We provide a discussion of the bulk viscosity of two-flavor quark plasma, described by the Nambu--Jona-Lasinio model, within the framework of Kubo-Zubarev formalism. This discussion, which is complementary to our earlier study, contains a new, detailed derivation of the bulk viscosity in the case of multiple conserved charges. We also provide some numerical details of the computation of the bulk viscosity close to the Mott transition line, where the dissipation is dominated by decays of mesons into quarks and their inverse processes. We close with a summary of our current understanding of this…
The productions of real photons from quark gluon plasma and hot hadronic matter formed after the nucleus - nucleus collisions at ultra-relativistic energies are discussed. The effects of the spectral shift of the hadrons at finite temperature on the production of photons are investigated. On the basis of the present analysis it is shown that the photon spectra measured by WA98 collaboration in Pb + Pb collisions at CERN SPS energies can be explained by both QGP as well as hadronic initial states if the spectral shift of hadrons at finite temperature is taken into account. Several other works o…
We introduce a combined macroscopic/microscopic transport approach employing relativistic hydrodynamics for the early, dense, deconfined stage of the reaction and a microscopic non-equilibrium model for the later hadronic stage where the equilibrium assumptions are not valid anymore. Within this approach we study the dynamics of hot, bulk QCD matter, which is expected to be created in ultra-relativistic heavy ion collisions at the SPS, the RHIC and the LHC. Our approach is capable of self-consistently calculating the freeze-out of the hadronic system, while accounting for the collective flow o…
The L-dependence of the static potential between Nc quarks arranged in a circle of radius L (a "baryon") immersed in the hot plasma of a gauge theory with Nc colors defines a screening length Ls. We use the AdS/CFT correspondence to compute this screening length for the case of heavy quarks in the plasma of strongly coupled N=4 super Yang-Mills theory moving with velocity v relative to the baryon. We find that in the v -> 1 limit, Ls \propto (1-v^2)^{1/4}/T, and find that corrections to this velocity dependence are small at lower velocities. This result provides evidence for the robustness of …
The Debye mass m_D is computed nonperturbatively in the deconfined phase of QCD, where chromomagnetic confinement is known to be present. The latter defines m_D to be m_D=c_D\sqrt{σ_s}, where c_D \approx 2 and σ_s=σ_s(T) is the spatial string tension. The resulting magnitude of m_D(T) and temperature dependence are in good agreement with lattice calculations.
We present the energy density and flux distribution of a heavy quark moving through high temperature QCD plasmas and compare them with those in the strongly coupled N = 4 SYM plasma. The Boltzmann equation is reformulated as a Fokker-Planck equation at the leading log approximation and is solved numerically with nontrivial boundary conditions in momentum space. We use kinetic theory and perform a Fourier transform to calculate the energy and momentum density in position space. The angular distributions exhibit the transition to the ideal hydrodynamics and are analyzed with the first and second…
We point out similarity of thermodynamic conditions reached in intermediate energy nuclear collisions and in supernova explosions. We show that a statistical approach, which has been previously applied for nuclear multifragmentation reactions, can be very useful for description of electro-neutral stellar matter. Then properties of hot unstable nuclei extracted from analysis of multifragmentation data can be used for construction of a realistic equation of state of supernova matter.
Structure of hot dense matter at subnuclear densities is investigated by quantum molecular dynamics (QMD) simulations. We analyze nucleon distributions and nuclear shapes using two-point correlation functions and Minkowski functionals to determine the phase-separation line and to classify the phase of nuclear matter in terms of the nuclear structure. Obtained phase diagrams show that the density of the phase boundaries between the different nuclear structures decreases with increasing temperature due to the thermal expansion of nuclear matter region. The critical temperature for the phase sepa…
