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 the order of 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=Wcphi= =0 during inflation (where W is the superpotential, the inflaton cphi, and W 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=Wcphi=0 automatic for =0. © 1995 The American Physical Society.