The momentum diffusion coefficient for heavy quarks is studied in a deconfined gluon plasma in the static approximation by investigating a correlation function of the color electric field using Monte~Carlo techniques. The diffusion coefficient is extracted from the long-distance behavior of such a correlator. For temperatures Tc<T$\lesssim${}2Tc, our nonperturbative estimate of the diffusion coefficient is found to be very different from the leading-order perturbation theory and is in the right ballpark to explain the heavy quark flow seen by the PHENIX Collaboration at the RHIC experiment.

We study the thermodynamics of $\mathrm{SU}(N_c)$ pure gauge theories for $N_c=3$, 4 and 6. The continuum and thermodynamic limits of bulk quantities such as the pressure ($p$), energy density ($ϵ$) and the entropy density ($s$) are taken by using several different lattice spacings and volumes. There is no window of temperature in which a nontrivial conformal theory describes bulk thermodynamics. We extract the latent heat of the first-order deconfinement phase transitions and observe good scaling with $N_c$. For all quantities that we measure, strong $N_c$ scaling holds, except, possibly, very close to the transition temperature, $T_c$; however we are unable to find strong evidence for scaling with the ’t Hooft coupling in thermal quantities at the small values of $N_c$ which we study. DOI: http://dx.doi.org/10.1103/PhysRevD.82.114505 © 2010 The American Physical Society

We report the measurement of quark number susceptibilities (QNS) and their temperature dependence from simulations of QCD with two flavors of light dynamical staggered quarks at finite temperature on $8\times 32^3$ lattices. From the radius of convergence of the Taylor expansion we estimate the critical end point. We use a Padé approximant to resum the series expansion and compute the equation of state at finite chemical potential, namely the baryon number density and its contribution to the pressure. We also report the isothermal compressibility of QCD matter at finite baryon density. Finally we explore the freeze-out conditions for a measure of fluctuations. We examine some sources of systematic and statistical errors in all of these measurements.

A thermal potential can be defined to facilitate understanding the behavior of quarkonia in quark-gluon plasma. A nonperturbative evaluation of this potential from lattice QCD is difficult, as it involves a real-time correlation function, and has often involved the use of Bayesian analysis, with its associated systematics. In this work we show that using the properties of the static quarkonia thermal correlation functions, one can directly extract a thermal potential for quarkonia from Euclidean Wilson loop data. This leads to a controlled extraction and allows us to judge the suitability of various model potentials.

Heavy quarks placed within a hot QCD medium undergo Brownian motion, characterized by specific transport coefficients. Their determination can be simplified by expanding them in T/M, where T is the temperature and M is a heavy quark mass. The leading term in the expansion originates from the colour-electric part of a Lorentz force, whereas the next-to-leading order involves the colour-magnetic part. We measure a colour-magnetic 2-point correlator in quenched QCD at T ∼ (1.2 − 2.0)T_c. Employing multilevel techniques and non-perturbative renormalization, a good signal is obtained, and its continuum extrapolation can be estimated. Modelling the shape of the corresponding spectral function, we subsequently extract the momentum diffusion coefficient, κ. For charm (bottom) quarks, the magnetic contribution adds ∼ 30% (10%) to the electric one. The same increases apply also to the drag coefficient, η. As an aside, the colour-magnetic spectral function is computed at NLO.