Constraining gravitational wave amplitude birefringence with GWTC-3

TL;DR

This paper searches for amplitude birefringence in gravitational waves using GWTC-3 data, providing the most precise constraints to date and testing for parity violations predicted by theories like Chern-Simons gravity.

Contribution

It introduces birefringent templates based on dynamical Chern-Simons gravity to analyze GWTC-3 data for amplitude birefringence, setting new constraints on parity violations in gravity.

Findings

Most precise constraints on gravitational-wave amplitude birefringence to date.

Measured birefringent attenuation parameter κ with 90% credibility.

Established lower bounds on parity-violation energy scale M_PV.

Abstract

The propagation of gravitational waves can reveal fundamental features of the structure of spacetime. For instance, differences in the propagation of gravitational-wave polarizations would be a smoking gun for parity violations in the gravitational sector, as expected from birefringent theories like Chern-Simons gravity. Here we look for evidence of amplitude birefringence in the third catalog of detections by the Laser Interferometer Gravitational Wave Observatory and Virgo through the use of birefringent templates inspired by dynamical Chern-Simons gravity. From $71$ binary-black-hole signals, we obtain the most precise constraints on gravitational-wave amplitude birefringence yet, measuring a birefringent attenuation of $\kappa = -0.019^{+0.038}_{-0.029} \, \mathrm{Gpc}^{-1}$ at $100 \, \mathrm{Hz}$ with $90\%$ credibility, equivalent to a parity-violation energy scale of $M_{\rm PV} \gtrsim 6.8 \times 10^{-21}\, {\rm GeV}$.