The effect of screening mechanisms on black hole binary inspiral waveforms

TL;DR

This paper investigates how screening mechanisms in scalar-tensor theories affect gravitational waveforms from black hole binaries, deriving corrections to GR predictions and assessing their detectability with current and future GW detectors.

Contribution

It introduces a scaling method for post-Newtonian expansion in screened regimes and calculates leading-order corrections to GW waveforms from binary black hole inspirals.

Findings

GW amplitude deviations are up to 1 part in 100 in the radiation zone

Corrections in the near zone are as small as 1 part in 10^{11}

Modifications are likely undetectable by current GW detectors but may be observable in future experiments.

Abstract

Scalar-tensor theories leaving significant modifications of gravity at cosmological scales rely on screening mechanisms to recover General Relativity (GR) in high-density regions and pass stringent tests with astrophysical objects. Much focus has been placed on the signatures of such modifications of gravity on the propagation of gravitational waves (GWs) through cosmological distances while typically assuming their emission from fully screened regions with the wave generation strictly abiding by GR. Here, we closely analyse the impact of screening mechanisms on the inspiral GW waveforms from compact sources by employing a scaling method that enables a post-Newtonian (PN) expansion in screened regimes. Particularly, we derive the leading-order corrections to a fully screened emission to first PN order in the near zone and we also compute the modifications in the unscreened radiation zone to second PN order. For a concrete example, we apply our results to a cubic Galileon model. The resulting GW amplitude from a binary black hole inspiral deviate from its GR counterpart at most by one part in $10^{2}$ for the modifications in the radiation zone and at most one part in $10^{11}$ due to next-order corrections to the fully screened near zone. We expect such modifications to be undetectable by the current generation of GW detectors, but the deviation is not so small as to remain undetectable in future experiments.