Little Inflatons and Gauge Inflation

Abstract

Cosmological inflation gives a natural answer for a variety of cosmological questions, including the horizon problem, the flatness problem, and others. However, inflation yields new questions relating to the flatness of the inflaton potential. Recent studies of ``little'' fields, a special class of pseudo-Goldstone bosons, have shown it is possible to protect the mass of a field while still yielding order one interactions with other fields. In this paper, we will show that ``little inflatons'' are natural candidates for the slow roll field of hybrid inflation models. We consider both supersymmetric and non-supersymmetric models, and give a simple examples based on approximate Abelian symmetries which solve the inflaton flatness problem of supergravity. We also present hybrid models in which components of gauge fields in higher dimensions play the role of the inflaton. Protected by higher-dimensional gauge symmetry, they, too, naturally have large couplings while suppressed mass terms. We summarize the implications of the new WMAP data on such models.