Do neutrino flavor oscillations forbid large lepton asymmetry of the universe?

It is shown that hypothetical neutrino-majoron coupling can suppress neutrino flavor oscillations in the early universe, in contrast to the usual weak interaction case. This reopens a window for a noticeable cosmological lepton asymmetry which is forbidden for the large mixing angle solution in the case of standard interactions of neutrinos. (C) 2004 Elsevier B.V. All rights reserved.