Gravity Waves as a Probe of Hubble Expansion Rate During An Electroweak Scale Phase Transition

TL;DR

This paper explores how gravitational wave measurements from electroweak scale phase transitions can serve as a probe of the universe's expansion rate at that epoch, similar to nucleosynthesis constraints at lower temperatures.

Contribution

It derives a transformation rule for gravitational wave spectra under changes in the Hubble expansion rate and applies it to a quintessence kination scenario.

Findings

Gravity wave spectra shift with the Hubble rate changes.

The transformation rule enables mapping of spectra across different expansion histories.

Predicted signals could be detectable by LISA and BBO.

Abstract

Just as big bang nucleosynthesis allows us to probe the expansion rate when the temperature of the universe was around 1 MeV, the measurement of gravity waves from electroweak scale first order phase transitions may allow us to probe the expansion rate when the temperature of the universe was at the electroweak scale. We compute the simple transformation rule for the gravity wave spectrum under the scaling transformation of the Hubble expansion rate. We then apply this directly to the scenario of quintessence kination domination and show how gravity wave spectra would shift relative to LISA and BBO projected sensitivities.