Polarization test of gravitational waves from compact binary coalescences

TL;DR

This paper investigates the ability of current and future gravitational wave detector networks to distinguish between different polarization modes of gravitational waves from binary coalescences, which can reveal the underlying theory of gravity.

Contribution

It systematically analyzes the separability of gravitational wave polarization modes in binary coalescence signals using multiple detectors, considering binary parameters and network configurations.

Findings

Three polarization modes are partially separable with three detectors.

Four detectors improve polarization mode separation and can distinguish all four modes.

Detection sensitivity and signal duration affect polarization mode distinguishability.

Abstract

Gravitational waves have only two polarization modes in General Relativity. However, there are six possible modes of polarization in metric theory of gravity in general. The tests of gravitational waves polarization can be tools for pursuing the nature of space-time structure. The observations of gravitational waves with a world-wide network of interferometric detectors such as Advanced LIGO, Advanced Virgo and KAGRA will make it possible to obtain the information of gravitational wave polarization from detector signals. We study the separability of the polarization modes for the inspiral gravitational waves from the compact binary coalescences systematically. Unlike other waveforms such as burst, the binary parameters need to be properly considered. We show that the three polarization modes of the gravitational waves would be separable with the global network of three detectors to some extent, depending on signal-to-noise ratio and the duration of the signal. We also show that with four detectors the three polarization modes would be more easily distinguished by breaking a degeneracy of the polarization modes and even the four polarization modes would be separable.