The Gelaton Scenario: Equilateral non-Gaussianity from multi-field dynamics

Abstract

The distinctive features of single field inflationary models with non-minimal kinetic terms, like Dirac-Born-Infeld and k-inflation, can be captured by more familiar multiple field inflationary systems of the type that typically arise in low energy supergravity models. At least one heavy field, which we call the gelaton, has an effective potential which depends on the kinetic energy of the inflaton. Integrating out the gelaton gives rise to an effectively single field system for which the speed of sound for the adiabatic fluctuations is reduced, generating potentially observable equilateral non-Gaussianity, while causing negligible isocurvature fluctuations. This mechanism is only active if there is a relatively tight coupling between the gelaton and the inflaton, and this puts an upper limit on the mass of the gelaton for which the inflaton-gelaton system remains weakly coupled. This approach gives a UV-completable framework for describing large classes of k-inflationary behavior.