The entropy of the QCD plasma

by E. IANCU (CERN)

Thursday 16 Sept 1999, 14:00 → 14:15 Europe/Zurich

TH Auditorium (CERN)

Asymptotic freedom suggests, and lattice calculations confirm, that at sufficiently high temperature or density, QCD should behave as a plasma of weakly interacting quarks and gluons. It thus appears as a surprise that the straight-forward perturbative expansion of the pressure is very poorly convergent, and does not seem to be of any quantitative use for all temperatures of interest. I argue that such a poor convergence is to be related to large collective effects, which should not be expanded in powers of a. I present a self-consistent calculation in terms of fully dressed propagators which provides a simple expression for the entropy in terms of the elementary excitations. This offers an accurate description of lattice data for purely gluonic QCD, down to temperatures of about 2T_c. By extending this to finite chemical potential, there where lattice calculations are not available, I make predictions for the QCD equation of state at large density.