  The decay of a false vacuum of unbroken B-L symmetry is an intriguing and
testable mechanism to generate the initial conditions of the hot early
universe. If B-L is broken at the grand unification scale, the false vacuum
phase yields hybrid inflation, ending in tachyonic preheating. The dynamics of
the B-L breaking Higgs field and thermal processes produce an abundance of
heavy neutrinos whose decays generate entropy, baryon asymmetry and gravitino
dark matter. We study the phase transition for the full supersymmetric Abelian
Higgs model. For the subsequent reheating process we give a detailed
time-resolved description of all particle abundances. The competition of cosmic
expansion and entropy production leads to an intermediate period of constant
'reheating' temperature, during which baryon asymmetry and dark matter are
produced. Consistency of hybrid inflation, leptogenesis and gravitino dark
matter implies relations between neutrino parameters and superparticle masses.
In particular, for a gluino mass of 1 TeV, we find a lower bound on the
gravitino mass of 10 GeV.
