Exploring the CPT violation and birefringence of gravitational waves with ground- and space-based gravitational-wave interferometers

Sai Wang

doi:10.1140/epjc/s10052-020-7812-2

Abstract

In the gravitational sector, we study the CPT violation and birefringence in gravitational waves. In presence of the CPT violation, a relative dephasing is generated between two circular polarization states of gravitational waves. This effect induces the birefringence of gravitational waves. Given the gravitational waveform modified by the CPT violation, we estimate the expected constraints on the CPT violation from Advanced Laser Interferometer Gravitational-Wave Observatory, Einstein Telescope and Laser Interferometer Space Antenna.

Highlights

In special relativity, the Lorentz symmetry is a fundamental invariance of physical laws in Minkowski spacetime
At extremely high energy scales, gravitational Lorentz symmetry is expected to be broken in theories of quantum gravity, such as deformed special relativity [2,3,4,5], Horava-Lifshitz gravity [6], loop quantum gravity [7,8], non-commutative geometry [9,10], superstring theory [11], etc
We explored the influences on the propagation of gravitational waves (GWs) from the CPT violation and birefringence in the gravitational sector [14,27,32]

Summary

Introduction

The Lorentz symmetry is a fundamental invariance of physical laws in Minkowski spacetime. A dispersion relation is split into two branches which are related to the two circular polarization states, respectively This implies that the two modes have a relative group velocity, which leads to an arrival-time difference between them in temporal domain. GW170817 has placed the most stringent constraints on the difference between the Lorentz-violating coefficients of mass dimension four in gravitational and photon sectors [22] This existing study is based on multi-messenger measurements of a relative group velocity of GWs and electromagnetic waves. By introducing the CPT-violating dispersion in SME, we will explore impacts of the birefringence on propagations of the two circular polarizations of GWs, which are emitted by distant astrophysical sources, and obtain corresponding modifications to GR gravitational waveform by following Refs.

Deformations of gravitational waveform due to the CPT violation

Fisher information matrix

Conclusions and discussion