Baryogenesis from a Chern-Simons condensate

Abstract

We study a new mechanism of baryon asymmetry generation at the electroweak scale proposed by Shaposhnikov. We give an alternative derivation of the effective action in the presence of background fermion density by showing that the gauge current becomes anomalous in a finite-chemical-potential background. We distinguish between the (physically irrelevant) change in the Chern-Simons number due to large gauge transformations and the (physically relevant) change in it due to a finite chemical potential. At high temperatures, ΔB created by tunneling between gauge-invariant vacua can be stored as a Chern-Simons condensate. At the phase transition, this state becomes unstable, but naively it decays to (a gauge transform of) the trivial vacuum with the same Chern-Simons number and hence no baryons are produced.