Searching For Gravitational Waves From Cosmological Phase Transitions With The NANOGrav 12.5-year dataset

TL;DR

This paper searches for gravitational wave signals from early universe phase transitions in pulsar timing data, finding potential signals at low temperatures but no definitive evidence, and discusses future prospects for detection.

Contribution

It introduces a search for gravitational waves from cosmological phase transitions using pulsar timing data and assesses the current and future detectability of such signals.

Findings

Data can be modeled by a strong first order phase transition below the electroweak scale.

No strong preference for phase transition signals over black hole mergers.

Future datasets could improve detection sensitivity and discrimination.

Abstract

We search for a first-order phase transition gravitational wave signal in 45 pulsars from the NANOGrav 12.5 year dataset. We find that the data can be modeled in terms of a strong first order phase transition taking place at temperatures below the electroweak scale. However, we do not observe any strong preference for a phase-transition interpretation of the signal over the standard astrophysical interpretation in terms of supermassive black holes mergers; but we expect to gain additional discriminating power with future datasets, improving the signal to noise ratio and extending the sensitivity window to lower frequencies. An interesting open question is how well gravitational wave observatories could separate such signals.