Inflation-produced magnetic fields in RnF2 and IF2 models

We reanalyze the production of seed magnetic fields during inflation in (R/m2)nFμνFμν and IFμνFμν models, where n is a positive integer, R the Ricci scalar, m a mass parameter, and Iηα a power-law function of the conformal time η, with α a positive real number. If m is the electron mass, the produced fields are uninterestingly small for all n. Taking m as a free parameter, we find that, for n≥2, the produced magnetic fields can be sufficiently strong in order to seed the dynamo mechanism and then to explain galactic magnetism. For α 2, there is always a window in the parameters defining inflation such that the generated magnetic fields are astrophysically interesting. Moreover, if inflation is (almost) de Sitter and the produced fields almost scale invariant (α 4), their intensity can be strong enough to directly explain the presence of microgauss galactic magnetic fields. © 2008 The American Physical Society.