Probing the equation of state of the early universe with a space laser interferometer

TL;DR

This paper proposes using a space laser interferometer to analyze the stochastic gravitational wave background from inflation, aiming to determine the early universe's equation of state and its evolution.

Contribution

It introduces a novel method to probe the early universe's equation of state through gravitational wave spectrum analysis, highlighting sensitivity to deviations from radiation domination.

Findings

Detects deviations from $w=1/3$ in the gravitational wave spectrum

Provides a new observational approach to early universe physics

Enhances understanding of inflationary gravitational waves

Abstract

We propose a method to probe the equation of state of the early universe and its evolution, using the stochastic gravitational wave background from inflation. A small deviation from purely radiation dominated universe ($w= 1/3$) would be clearly imprinted on the gravitational wave spectrum $\Omega_{GW}(f)$ due to the nearly scale invariant nature of inflationary generated waves.