Search for anisotropic, birefringent spacetime-symmetry breaking in gravitational wave propagation from GWTC-3

TL;DR

This paper uses gravitational wave data from GWTC-3 to search for signs of spacetime anisotropy and birefringence caused by Lorentz and CPT violation, setting new bounds on these effects.

Contribution

It introduces a Bayesian analysis framework to constrain anisotropic and birefringent dispersion effects in gravitational waves using LIGO-Virgo-KAGRA data.

Findings

Maximal bound of 3.19 x 10^{-15} m on isotropic coefficient

Limits of order 10^{-13} m on anisotropic coefficients

Robustness analysis shows waveform modeling impacts constraints

Abstract

An effective field theory framework, the Standard-Model Extension, is used to investigate the existence of Lorentz and CPT-violating effects during gravitational wave propagation. We implement a modified equation for the dispersion of gravitational waves, that includes isotropic, anisotropic and birefringent dispersion. Using the LIGO-Virgo-KAGRA algorithm library suite, we perform a joint Bayesian inference of the source parameters and coefficients for spacetime symmetry breaking. From a sample of 45 high confidence events selected in the GWTC-3 catalog, we obtain a maximal bound of $3.19 \times 10^{-15}$~m at 90\% CI for the isotropic coefficient $k_{(V)00}^{(5)}$ when assuming the anisotropic coefficients to be zero. The combined measurement of all the dispersion parameters yields limits on the order of $10^{-13}$~m for the 16 $k_{(V)ij}^{(5)}$ coefficients. We study the robustness of our inference by comparing the constraints obtained with different waveform models, and find that a lack of physics in the simulated waveform may appear as spacetime symmetry breaking-induced dispersion for a subset of events.