Minimal warm inflation with complete medium response

TL;DR

This paper introduces a comprehensive framework for modeling warm inflation by accounting for all medium time scales, demonstrated through a thermal Yang-Mills plasma example, revealing the system's heating and inflation regimes.

Contribution

It presents a novel framework that incorporates all medium time scales into warm inflation modeling, improving upon previous approximate methods.

Findings

System heats up and enters weak or strong warm inflation regimes

Framework successfully describes axion inflation with thermal medium effects

Scrutinizes and improves previous approximate treatments

Abstract

If a homogeneous field evolves within a medium, with the latter gradually picking up a temperature, then the friction felt by the field depends on how its evolution rate compares with medium time scales. We suggest a framework which permits to incorporate the contributions from all medium time scales. As an example, we illustrate how warm axion inflation can be described by inputting the retarded pseudoscalar correlator of a thermal Yang-Mills plasma. Adopting a semi-realistic model for the latter, and starting the evolution at almost vanishing temperature, we show how the system heats up and then enters the "weak" or "strong" regime of warm inflation. Previous approximate treatments are scrutinized.