ON FINITE-TEMPERATURE AND FINITE-DENSITY RADIATIVE-CORRECTIONS TO THENEUTRINO EFFECTIVE POTENTIAL IN THE EARLY UNIVERSE

Finite-temperature and finite-density radiative corrections to the neu trino effective potential in the otherwise CP-symmetric early Universe are considered in the real-time approach of thermal field theory. A c onsistent perturbation theory endowed with the hard thermal loop resum mation techniques developed by Braaten and Pisarski is applied. Specia l attention is focused on the question whether such corrections can ge nerate any nonzero contribution to the CP-symmetric part of the neutri no potential, if the contact approximation for the W-propagator is use d.