  Late-time entropy production from scalar decay arises in scenarios like
thermal inflation, proposed to dilute long-lived, massive fields like the
gravitino and the moduli. The scalar decay may continue into Mev-scale
temperatures and affect BB nucleosynthesis. The effect of such entropy
production on electron neutrino decoupling is studied. A lower bound of about
10^(-22) Gev is estimated for the scalar decay constant, such that, for higher
values of the decay constant, standard electron neutrino decoupling is
unaffected.
