The Chiral Phase Transition and Instanton Anti-instanton Molecules

We explore the idea that the chiral phase transition in QCD can be described as a transition from a disordered instanton liquid to a strongly correlated phase of polarized instanton anti-instanton molecules. We find a number of non perturbative effects caused by the presence of instantons above T_c, among them the fact that instantons contribute to the euquation of state. We also study how instantons affect the propagation of light quarks at high temperature and determine the spacelike screening masses for mesons and baryons. We derive the corresponding effective interaction and find that the interaction in the scalar-pseudoscalar channel is attractive and four times stronger than the one in the vector-axial-vector channel, in agreement with recent lattice QCD simulations.