THE QCD VACUUM, CHIRAL PHASE TRANSITION AND QUARK-GLUON PLASMA

Abstract

In recent years, significant progress was reached in understanding of vacuum and hadronic structure. We review recent works on the {\it point-to-point correlation functions}, comparing those obtained from phenomenology, ``instanton liquid" models and on the lattice. The second topic is physics of chiral symmetry restoration, which may lead to observable hadron modification and unusual event-per-event fluctuations. We discuss collective flow and phenomena related with a remarkable ``softness" of the equation of state near the phase transition, as well as phenomena at small $p_t$. We also describe recent ideas on the mechanism of chiral restoration, based on formation of {\it polarized instanton-antiinstanton molecules}. The third part, related to quark-gluon plasma, is related mainly with the issue of initial equilibration of QGP in high energy collisions. We discuss different ``parton cascade" approaches and argue that {\it multi-gluon} processes dominate them. We briefly discuss predictions for RHIC and LHC energies.