Quasi-instantons in QCD with chiral symmetry restoration

Abstract

We show, without using semiclassical approximations, that, in high-temperature QCD with chiral symmetry restoration and ${\mathrm{U}(1)}_{\mathrm{A}}$ symmetry breaking, the partition function for sufficiently light quarks can be expressed as an ensemble of noninteracting objects with topological charge that obey the Poisson statistics. We argue that the topological objects are ``quasi-instantons'' (rather than bare instantons) taking into account quantum effects. Our result is valid even close to the (pseudo)critical temperature of the chiral phase transition.