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

TL;DR

This paper introduces a multi-field inflationary model involving a heavy gelaton field that, when integrated out, produces an effectively single-field system with reduced sound speed, leading to observable equilateral non-Gaussianity.

Contribution

It presents a novel multi-field inflationary framework with a gelaton field that explains non-Gaussianity through effective single-field dynamics derived from UV-complete models.

Findings

Reduced sound speed causes observable non-Gaussianity

Heavy gelaton field influences inflationary dynamics

Framework is compatible with UV-completion

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.