Chiral Current at High Temperatures

Abstract

The BP-FTW effective action is a good laboratory to study the nature of chiral symmetry at high $T$. It is invariant under a new Noether charge, $\Qbeta$. By explicit quantization, performed to order $\Tprime$ we show that the thermal vacuum is annihilated by $\Qbeta$, so that the new chiral symmetry is not broken spontaneously at high $T$. This high $T$ Noether charge is, however, different from the usual zero temperature chirality, $\Q$. Our quantization also shows that the thermal vacuum is not annihilated by $\Q$, so that the old chiral symmetry remains broken at high $T$. The thermal vacuum is thus every bit as `structured' and `complex' as the Nambu-Jona-Lasinio vacuum at zero temperature. We exhibit the relation between the normal mode expansion for $\Qbeta$ versus the usual expansion for $\Q$. In an appendix, we point out the analyticity properties of the fermion propagator in real time formalism, and verify the canonical nature of the thermal Green function.