Tests of CPT invariance in gravitational waves with LIGO-Virgo catalog GWTC-1

Abstract

Abstract A discovery of gravitational waves from binary black holes raises a possibility that measurements of them can provide strict tests of CPT invariance in gravitational waves. When CPT violation exists, if any, gravitational waves with different circular polarizations could gain a slight difference in propagating speeds. Hence, the birefringence of gravitational waves is induced and there should be a rotation of plus and cross modes. For CPT-violating dispersion relation $${\omega ^{2}=k^{2}}$$ ω 2 = k 2 $${\pm 2\zeta k^{3}}$$ ± 2 ζ k 3 , where a sign $${\pm }$$ ± denotes different circular polarizations, we find no substantial deviations from CPT invariance in gravitational waves by analyzing a compilation of ten signals of binary black holes in the LIGO-Virgo catalog GWTC-1. We obtain a strict constraint on the CPT-violating parameter, i.e., $$\zeta =0.14^{+0.22}_{-0.31}\times 10^{-15}\,\text {m}$$ ζ = 0 . 14 - 0.31 + 0.22 × 10 - 15 m , which is around two orders of magnitude better than the existing one. Therefore, this study stands for the up-to-date strictest tests of CPT invariance in gravitational waves.