Broken symmetries

Abstract

Recalling the relation between critical behavior and spontaneous symmetry breaking, we show that deconfinement in SU(N) gauge theory is based on the breaking of a global ZN symmetry. Next we turn to the chiral symmetry of the QCD Lagrangian in case of massless quarks and discuss the spontaneous breaking and eventual restoration of this symmetry. We then consider the relation of the two kinds of symmetry breaking in determining the transition behavior as well as the general transition pattern as a function of the input quark masses.