Sphalerons and baryogenesis: Electroweak CP violation at high temperatures

The effective action for the gauge fields in the electroweak plasma of the early Universe is considered. It is argued that in thermal equilibrium the effective action contains a CP-odd term proportional to the Chern-Simons number density provided the exactly conserved fermionic charges Li-B/nf are nonzero (Li are leptonic generations numbers, B is baryonic charge). In order to obtain the non-equilibrium distributions of fermions in the expanding Universe, the relevant kinetic equations involving both the electroweak CP-violation effects and the anomalous fermion number non-conservation are derived and solved. It is found that the Kobayashi-Maskawa CP-violation is sufficient to ensure the validity of the electroweak (EW) scenario of baryogenesis. We elaborate the program for the determination of the sign of the baryon asymmetry and discuss the interplay between GUT and EW scenarios. (orig.)