Search for the birefringence of gravitational waves with the third observing run of Advanced LIGO-Virgo

TL;DR

This paper uses data from Advanced LIGO-Virgo's third observing run to set the most stringent limits yet on gravitational wave birefringence, testing CPT symmetry at the 10 GeV scale and finding no evidence for birefringence.

Contribution

It provides the first 10 GeV-scale test of CPT symmetry in gravitational waves by constraining birefringence with the latest LIGO-Virgo data.

Findings

Set the strictest limit on CPT-violating birefringence parameter, ζ.

Bayes factor analysis disfavours the birefringence scenario.

Achieved a limit five times stricter than previous bounds.

Abstract

Gravitational waves would attain birefringence during their propagation from distant sources to the Earth, when the CPT symmetry is broken. If it was sizeable enough, such birefringence could be measured by the Advanced LIGO, Virgo and KAGRA detector network. In this work, we place constraints on the birefringence of gravitational waves with the third observing run of this network, i.e. two catalogues GWTC-2 and GWTC-3. For the dispersion relation $\omega^{2}=k^{2}\pm2\zeta k^{3}$, our analysis shows the up-to-date strictest limit on the CPT-violating parameter, i.e. \textcolor{black}{{$\zeta=4.07^{+5.91}_{-5.79}\times10^{-17}\mathrm{m}$}}, at $68\%$ confidence level. This limit is stricter by $\sim$5 times than the existing one {($\sim 2\times10^{-16}$m)} and stands for the first $\sim$10GeV-scale test of the CPT symmetry in gravitational waves. The results of Bayes factor strongly disfavor the birefringence scenario of gravitational waves.