Chiral Morphing

Abstract

Chiral symmetry undergoes a metamorphosis at T c . For T < T c , the usual Noether charge, Q a 5 , is dynamically broken by the vacuum. Above T c , chiral symmetry undergoes a subtle change, and the Noether charge morphs into Q β 5 , with the thermal vacuum now becoming invariant under Q β 5 .This vacuum is however not invariant under the old Q a 5 transformations. As a result, the pion remains strictly massless at high T . The pion propagates in the early universe with a halo.New order parameters are proposed to probe the structure of the new thermal vacuum.