Quest for the Quark-Gluon Plasma

Present status and future prospect of the quest for the quark-gluon plasma with untrarelativistic nuclear collisions are discussed.Comment: Invited talk given at Tokyo-Adelaide Joint Workshop on Quarks, Astrophysics, Space Physics, University of Tokyo, Jan.6 -10, 200

Boost invariant quantum evolution of a meson field at large proper times

We construct asymptotic solutions of the functional Schroedinger equation for a scalar field in the Gaussian approximation at large proper time. These solutions describe the late proper time stages of the expansion of a meson gas with boost invariant boundary conditions. The relevance of these solutions for the formation of a disoriented chiral condensate in ultra relativistic collisions is discussed.Comment: 9 pages, LATE

Chiral Phase Transition at Finite Temperature in the Linear Sigma Model

We study the chiral phase transition at finite temperature in the linear sigma model by employing a self-consistent Hartree approximation. This approximation is introduced by imposing self-consistency conditions on the effective meson mass equations which are derived from the finite temperature one-loop effective potential. It is shown that in the limit of vanishing pion mass, namely when the chiral symmetry is exact, the phase transition becomes a weak first order accompanying a gap in the order parameter as a function of temperature. This is caused by the long range fluctuations of meson fields whose effective masses become small in the transition region. It is shown, however, that with an explicit chiral symmetry breaking term in the Lagrangian which generates the realistic finite pion mass the transition is smoothed out irrespective of the choice of coupling strength.Comment: 21 pages, Late