  We consider a minimal supersymmetric extension of the Standard Model, with
right-handed neutrinos and local B-L, the difference between baryon and lepton
number, a symmetry which is spontaneously broken at the scale of grand
unification. To a large extent, the parameters of the model are determined by
gauge and Yukawa couplings of quarks and leptons. We show that this minimal
model can successfully account for the earliest phases of the cosmological
evolution: Inflation is driven by the energy density of a false vacuum of
unbroken B-L symmetry, which ends in tachyonic preheating, i.e. the decay of
the false vacuum, followed by a matter dominated phase with heavy B-L Higgs
bosons. Nonthermal and thermal processes produce an abundance of heavy
neutrinos whose decays generate primordial entropy, baryon asymmetry via
leptogenesis and dark matter consisting of gravitinos or nonthermal WIMPs. The
model predicts relations between neutrino and superparticle masses and a
characteristic spectrum of gravitational waves.
