Inflation, supergravity, and superstrings.

The positive potential energy required for inflation spontaneously breaks supersymmetry and in general gives any would-be inflaton an effective mass of order the inflationary Hubble parameter thus ruling it out as an inflaton. In this paper I give simple conditions on the superpotential that eliminate some potential sources for this mass, and derive a form for the Kähler potential that eliminates the rest. This reduces the problem of constructing a model of inflation in supergravity to that of constructing one in global supersymmetry with the extra conditions W = Wφ = ψ = 0 during inflation (where W is the superpotential, the inflaton ∈ φ, and Wψ 6= 0). I then point out that Kähler potentials of the required form often occur in superstrings and that the target space duality symmetries of superstrings often contain R-parities which would make W = Wφ = 0 automatic for ψ = 0. KUNS 1261 hep-ph/9405389