Accelerated expansion in the effective field theory of a radiation dominated universe

TL;DR

This paper develops an effective field theory for a radiation-dominated universe, revealing possible accelerated expansion phases like inflation and bounce, driven by fluid corrections beyond gravity alone.

Contribution

It introduces a novel EFT framework for radiation fluids in the early universe, highlighting their role in inducing accelerated expansion.

Findings

Identification of inflationary solutions within the EFT of radiation

Discovery of bounce solutions driven by fluid corrections

Demonstration of regimes where fluid effects dominate over gravity

Abstract

We construct the effective field theory of a perfect fluid in the early universe. Focusing on the case where the fluid has the equation of state of radiation, we show that it may lead to corrections to the background dynamics that can dominate over those of an effective field theory of gravity alone. We describe the periods of accelerated expansion, in the form of inflationary and bounce solutions, that arise in the background dynamics and discuss their regime of validity within EFT.