arXiv subjects
Publications and source records attributed to Frithjof Karsch.
We discuss results from lattice calculations for a few observables that are sensitive to different length scales in the high temperature phase of QCD and can give insight into its non-perturbative structure. We compare lattice results with perturbative calculations at high temperature obtained for vanishing and non-vanishing quark chemical potential.
At high temperatures or densities matter formed by strongly interacting elementary particles (hadronic matter) is expected to undergo a transition to a new form of matter - the quark gluon plasma - in which elementary particles (quarks and gluons) are no longer confined inside hadrons but are free to propagate in a thermal medium much larger in extent than the typical size of a hadron. The transition to this new form of matter as well as properties of the plasma phase are studied in large scale numerical calculations based on the theory of strong interactions - Quantum Chromo Dynamics (QCD). Experimentally properties of hot and dense elementary particle matter are studied in relativistic heavy ion collisions such as those currently performed at the relativistic heavy ion collider (RHIC) at BNL. We review here recent results from studies of thermodynamic properties of strongly interacting elementary particle matter performed on Teraflops-Computer. We present results on the QCD equation of state and discuss the status of studies of the phase diagram at non-vanishing baryon number density.
We review recent progress in studies of bulk thermodynamics of strongly interacting matter, present results on the QCD equation of state and discuss the status of studies of the phase diagram at non-vanishing quark chemical potential.
Modifications in the production pattern of heavy quark bound states have long been considered to provide sensitive signatures for the thermal properties of dense matter created in heavy ion collisions. The original concept of Matsui and Satz for quarkonium suppression as signature for deconfinement in heavy ion collisions has been challenged recently through lattice studies of spectral functions, which indicate the persistence of heavy quark bound states at temperatures well above the transition, as well as through the refined analysis of hadronization and recombination models, which take into account the thermal evolution of the medium generated in a heavy ion collision. We will review here recent developments on these topics.
We present recent lattice results on QCD thermodynamics at non-vanishing baryon number density obtained from a 6th order Taylor expansion in the chemical potential. Results for bulk thermodynamic observables, in particular for fluctuations in the baryon number density, are found to be well described by a hadron resonance gas model at low temperature and an ideal quark gluon gas at high temperature. We also analyze the radius of convergence of the Taylor series and discuss the information it provides on the occurrence of a second order phase transition point in the QCD phase diagram.
Lattice studies of charmonium systems have indicated that in a deconfined gluonic plasma ground state charmonia survive as bound states upto temperatures \~ 2 Tc. After surveying the methodologies used in reaching these results, we examine the behavior of these systems when the bound state is in motion with respect to the heatbath frame. We find that the finite momenta charmonia show medium modifications when the medium is deconfined; in particular, a modification of the energy-momentum dispersion relation is indicated.
We discuss recent lattice results on in-medium properties of hadrons and focus on thermal properties of heavy quark bound states. We will clarify the relation between heavy quark free energies and potentials used to analyze the melting of heavy quark bound states. Furthermore, we present calculations of meson spectral functions which indicate that the charmonium ground states, J/psi and eta_c, persist in the quark gluon plasma as well defined resonances with no significant change of their zero temperature masses at least up to T ~ 1.5 T_c. We also briefly comment on the current status of lattice calculations at non-vanishing baryon number density.
The behavior of charmonia after the deconfinement transition is investigated on quenched lattices. Analysis of temporal correlators on fine lattices at temperatures upto 3 T_c show that the J/psi and eta_c survive the deconfinement transition with little significant changes, and survive as bound states at least upto 2.25 T_c. The spatially excited chi_c states suffer serious system modifications, maybe dissolution, already a little above T_c.
We present results from lattice calculations on the thermodynamics of QCD at non-zero temperature and baryon chemical potential and discuss the role of resonances for the occurrence of the transition to the quark-gluon plasma in hot and dense matter. Properties of a hadronic resonance gas are compared to lattice results on the equation of state at zero as well as non-zero baryon chemical potential. Furthermore, it is shown that the quark mass dependence of the transition temperature can be understood in terms of lines of constant energy density in a resonance gas.
We study the renormalized free energy of a heavy quark anti-quark pair in the different colour channels in full QCD at finite temperature. Similarities and differences to the quenched case are discussed and the temperature dependence as well as their short distance behavior are analyzed. The asymptotic large distance behavior of the free energy is used to define the non-perturbatively renormalized Polyakov loop which is well behaved in the continuum limit.
We present a study of charmonia in hot gluonic plasma, for temperatures upto three times the deconfinement transition temperature Tc. q \bar{q} systems with quark masses close to the charm mass and different spin-parity quantum numbers were studied on very fine isotropic lattices. The analysis of temporal correlators, and spectral functions constructed from them, shows that the J/psi and eta_c survive up to quite high temperatures, with little observable change up to 1.5 Tc, and then gradually weakening and disappearing by 3 Tc. For the scalar and axial vector channels, serious modifications are induced by the hot medium already close to Tc, possibly dissociating the mesons by 1.1 Tc.
We discuss the phase structure and the equation of state for QCD at non-zero temperature and density. Derivatives of $\ln Z$ with respect to quark chemical potential $μ_q$ up to fourth order are calculated for 2-flavor QCD, enabling estimates of the pressure, quark number density and associated susceptibilities as functions of $μ_q$ via a Taylor series expansion. Also, the phase transition line for 2 and 3-flavor QCD and the critical endpoint in the $(T, μ_q)$ plane are investigated in the low density regime.
We present results from lattice studies of charmonium systems near the deconfinement transition temperature. On quenched isotropic lattices with lattice spacings between 0.02 and 0.05 fm, bar{q} q systems with quark masses close to the charm mass and with different spin-parity quantum numbers are studied in the temperature range 0.9 Tc - 3 Tc. Results for temporal correlators of local operators, and the spectral functions constructed from them, are discussed. For the pseudoscalar and vector channels, the correlators are observed to change very little across the deconfinement transition, unlike in the case of the light quarks.
We study the κ^2 corrections to the quenched limit of μ>0 QCD. We use an improved reweighting procedure.
We discuss recent results on the thermodynamics of QCD in the presence of light dynamical quark degrees of freedom. In particular, we concentrate on an analysis of the flavour and quark mass dependence of the QCD phase diagram, the equation of state and the transition temperature. Moreover, we present recent results on the heavy quark free energy.
After a brief introduction into basic aspects of the formulation of lattice regularized QCD at finite temperature and density we discuss our current understanding of the QCD phase diagram at finite temperature. We present results from lattice calculations that emphasize the deconfining as well as chiral symmetry restoring features of the QCD transition, and discuss the thermodynamics of the high temperature phase.
We review recent results on QCD at finite temperature. Main emphasis is put on a discussion of observables which are of immediate interest to experimental searches for the Quark Gluon Plasma, i.e. the phase transition temperature, the equation of state in 2 and 3-flavour QCD, the heavy quark free energy and thermal effects on hadron masses.
We analyze the critical behaviour of the three-dimensional, three-state Potts model in the presence of an external ordering field. From a finite size scaling analysis on lattices of size up to 70**3 we determine the critical endpoint of the line of first order phase transitions as (b_c, h_c) =(0.54938(2), 0.000775(10)). We determine the relevant temperature like and symmetry breaking directions at this second order critical point and explicitly verify that it is in the universality class of the three-dimensional Ising model.