Searching for modified gravity in the astrophysical gravitational wave background: Application to ground-based interferometers

TL;DR

This paper explores how modifications in gravity theories, specifically Horndeski gravity, affect the astrophysical gravitational wave background and assesses the potential for ground-based interferometers to detect these effects, providing forecasts for constraining gravity models.

Contribution

It introduces a method to detect modifications in gravity through the amplitude correction of the AGWB and evaluates the sensitivity of current and future interferometers to these effects.

Findings

Significant AGWB signals detectable by ET and CE within 5 and 1 years.

Forecasted bounds of 27% and 18% on the Planck mass running from ET and CE.

Detection of AGWB can constrain gravity theories with high precision.

Abstract

We investigate how the propagation of an astrophysical gravitational wave background (AGWB) is modified over cosmological volumes when considering theories beyond general relativity of the type Horndeski gravity. We first deduce an amplitude correction on the AGWB induced for the presence of a possible running in the Planck mass. Then, we apply the spectral noise density from some ground-based interferometers, namely, the Advanced LIGO (aLIGO), Einstein Telescope (ET) and Cosmic Explore (CE), to evaluate the signal-to-noise ratio (SNR) as a function of the amplitude of the running of the Planck mass for two different scenarios. We find that for observation time period $\gtrsim$ 5 yrs and $\gtrsim$ 1 yr, we can have a significant signal of the AGWB in the band [1-100] Hz from the ET and CE sensitivity, respectively. Using Fisher information, we find some forecast bounds, and we deduce $\lesssim$ 27\% and $\lesssim$ 18\% correction at 1$\sigma$ confidence level on the amplitude of the running of the Planck mass from ET and CE, respectively. It is clear that a detection of a AGWB in future can open a new window to probe the nature of gravity with good accuracy.