Measuring the maximally allowed polarization states of the isotropic stochastic gravitational wave background with the ground-based detectors

TL;DR

This paper analyzes how ground-based gravitational wave detectors can measure the polarization states of an isotropic gravitational wave background, highlighting the impact of adding LIGO-India on sensitivity, especially for odd spectral components.

Contribution

It introduces a method to decompose polarization spectra using overlap reduction functions and identifies relations that affect this decomposition at low frequencies.

Findings

LIGO-India enhances sensitivity to odd spectral components.

Two relations between overlap reduction functions hinder decomposition at low frequencies.

Decomposition is feasible above 30 Hz with the current detector network.

Abstract

We discuss the polarizational study of isotropic gravitational wave backgrounds with the second generation detector network, paying special attention to the impacts of adding LIGO-India. The backgrounds can be characterized by at most five spectral components (three parity-even ones and two parity-odd ones). They can be algebraically decomposed through the difference of the corresponding overlap reduction functions defined for the individual spectra. We newly identify two interesting relations between the overlap reduction functions, and these relations generally hamper the algebraic decomposition in the low frequency regime $f \lesssim 30$Hz. We also find that LIGO-India can significantly improve the network sensitives to the odd spectral components.