Quarkonium at Finite Temperature

We discuss properties of heavy quarkonium states at high temperatures based on lattice QCD and potential models. We review recent progress made in lattice calculations of spatial static quark anti-quark correlators as well as quarkonium correlators in Euclidean time. Recent developments in effective field theory approach and potential models are also discussed.Comment: 50 pages, 30 figures, 2 tables; invited review for chapter in "Quark-Gluon Plasma

Static quark anti-quark pair in SU(2) gauge theory

We study singlet and triplet correlation functions of static quark anti-quark pair defined through gauge invariant time-like Wilson loops and Polyakov loop correlators in finite temperature SU(2) gauge theory. We use the Luescher-Weisz multilevel algorithm, which allows to calculate these correlators at very low temperatures. We observe that the naive separation of singlet and triplet states in general does not hold non-perturbatively, however, is recovered in the limit of small separation and the temperature dependence of the corresponding correlators is indeed very different.Comment: ReVTeX, 11 pages, 5 figure

Model A Dynamics and the Deconfining Phase Transition for Pure Lattice Gauge Theory

We consider model A dynamics for a heating quench from the disordered (confined) into the ordered (deconfined) phase of SU(3) lattice gauge theory. For $4 N_{\sigma}^3$ lattices the exponential growth factors of low-lying structure function modes are calculated. The linear theory of spinodal decompositions is compared with the data from an effective model and the Debye screening mass is estimated from the critical mode. Further, the quench leads to competing vacuum domains, which make the equilibration of the QCD vacuum after the heating non-trivial. We investigate the influence of such domains on the gluonic energy density.Comment: A talk presented at the Workshop on QCD in Extreme Environments (Argonne National Laboratory), 5 pages, 5 figure

Finite temperature SU(2) gauge theory: critical coupling and universality class

We examine SU(2) gauge theory in 3+1 dimensions at finite temperature in the vicinity of critical point. For various lattice sizes in time direction ($N_\tau=1,2,4,8$) we extract high precision values of the inverse critical coupling and critical values of the 4-th order cumulant of Polyakov loops (Binder cumulant). We check the universality class of the theory by comparing the cumulant values to that of the 3D Ising model and find very good agreement. The Polyakov loop correlators for the indicated lattices are also measured and the string tension values extracted. The high precision values of critical coupling and string tension allow us to study the scaling of dimensionless $T_c/\sqrt{\sigma}$ ratio. The violation of scaling by <10% is observed as the coupling is varied from weak to strong coupling regime.Comment: 17 pages, 9 figures, minor correction

Quarkonium Spectral Function from Anisotropic Lattice

We discuss the behavior of charmonia and bottomonia correlators and spectral functions above the deconfinement temperature and determine melting temperatures for different mesonic states.Comment: 4 pages, 6 figures. Talk presented at Hard Probes 2006, Asilomar, California, USA, June 9-16, 200

Equilibrium criterion and effective spin models for finite temperature gauge theories

Using the example of the SU(2) gauge theory in 3+1 dimensions we consider the construction of a 3-dimensional effective model in terms of Polyakov loops. We demonstrate the application of an equilibrium self-consistency condition to the systematic analysis of the contribution of various (global Z(2) symmetric) terms in the effective model action. We apply this analysis to the construction of a simple effective action with the minimum necessary number of operators. Such an action is shown to be capable of reproducing relevant observables, e.g. the Polyakov loop ensemble average, within the desired accuracy.Comment: 5 pages, 4 figures, minor correction