Dirac-Born-Infeld warm inflation realization in the strong dissipation regime

TL;DR

This paper explores how a low sound speed in Dirac-Born-Infeld warm inflation can suppress certain spectral features, enabling a strong dissipation regime that aligns well with string theory models.

Contribution

It demonstrates that low sound speed parameters facilitate the realization of strong dissipation warm inflation with DBI kinetic terms, easing theoretical constraints and supporting string theory embedding.

Findings

Low sound speed suppresses the scalar power spectrum growth.

Strong dissipation regime becomes more attainable with low sound speed.

Results support the compatibility of warm inflation with string theory frameworks.

Abstract

We consider warm inflation with a Dirac-Born-Infeld (DBI) kinetic term in which both the nonequilibrium dissipative particle production and the sound speed parameter slow the motion of the inflaton field. We find that a low sound speed parameter removes, or at least strongly suppresses, the growing function appearing in the scalar of curvature power spectrum of warm inflation, which appears due to the temperature dependence in the dissipation coefficient. As a consequence of that, a low sound speed helps to push warm inflation into the strong dissipation regime, which is an attractive regime from a model building and phenomenological perspective. In turn, the strong dissipation regime of warm inflation softens the microscopic theoretical constraints on cold DBI inflation. The present findings, along with the recent results from swampland criteria, give a strong hint that warm inflation may consistently be embedded into string theory.