Thermal Inflation and the Gravitational Wave Background

TL;DR

Thermal inflation in supersymmetric models can significantly dilute primordial gravitational waves at small scales but also produce a new, detectable stochastic gravitational wave background from bubble collisions, observable by future experiments like BBO.

Contribution

This paper analyzes how thermal inflation affects the gravitational wave background, highlighting the potential for bubble collision signals within BBO's detection range.

Findings

Primordial gravitational waves are diluted at small scales due to thermal inflation.

Bubble collisions generate a new stochastic gravitational wave background.

The predicted bubble collision signal falls within the sensitivity of BBO.

Abstract

We consider the impact of thermal inflation -- a short, secondary period of inflation that can arise in supersymmetric scenarios -- on the stochastic gravitational wave background. We show that while the primordial inflationary gravitational wave background is essentially unchanged at CMB scales, it is massively diluted at solar system scales and would be unobservable by a BBO style experiment. Conversely, bubble collisions at the end of thermal inflation can generate a new stochastic background. We calculate the likely properties of the bubbles created during this phase transition, and show that the expected amplitude and frequency of this signal would fall within the BBO range.