LISA Sensitivity to Gravitational Waves from Sound Waves

TL;DR

This paper evaluates LISA's sensitivity to gravitational waves from sound waves during early Universe phase transitions, using peak-integrated sensitivity curves to compare models and account for noise factors.

Contribution

It introduces a systematic method using PISCs to analyze LISA's sensitivity across multiple models, considering spectral shapes and galactic noise effects.

Findings

Galactic confusion noise reduces observable scenarios by about half.

LISA's sensitivity depends on data collection and spectral shape assumptions.

Numerical results are publicly available on Zenodo.

Abstract

Gravitational waves (GWs) produced by sound waves in the primordial plasma during a strong first-order phase transition in the early Universe are going to be a main target of the upcoming Laser Interferometer Space Antenna (LISA) experiment. In this short note, I draw a global picture of LISA's expected sensitivity to this type of GW signal, based on the concept of peak-integrated sensitivity curves (PISCs) recently introduced in [1909.11356, 2002.04615]. In particular, I use LISA's PISC to perform a systematic comparison of several thousands of benchmark points in ten different particle physics models in a compact fashion. The presented analysis (i) retains the complete information on the optimal signal-to-noise ratio, (ii) allows for different power-law indices describing the spectral shape of the signal, (iii) accounts for galactic confusion noise from compact binaries, and (iv) exhibits the dependence of the expected sensitivity on the collected amount of data. An important outcome of this analysis is that, for the considered set of models, galactic confusion noise typically reduces the number of observable scenarios by roughly a factor two, more or less independent of the observing time. The numerical results presented in this paper are also available on Zenodo [http://doi.org/10.5281/zenodo.3837877].