Distinguishing gravity theories with networks of space-based gravitational-wave detectors

TL;DR

This paper introduces a method to distinguish non-tensor gravitational-wave modes using space-based detector networks, enabling tests of alternative gravity theories through polarization mode detection in the mHz frequency band.

Contribution

The paper presents four data-reconstruction schemes for space-based detector configurations, demonstrating the effectiveness of the co-inclination setup in detecting vector and scalar modes of SGWBs.

Findings

Co-inclination configuration achieves higher signal-to-noise ratios.

Detection of vector modes with SNR up to 17.3.

Detection of scalar modes with SNR up to 10.4.

Abstract

We propose a method for separating and detecting the non-tensor modes of stochastic gravitational-wave backgrounds (SGWBs) using networks of space-based gravitational-wave detectors. We consider four distinct data-reconstruction schemes for the co-inclination and anti-inclination orbital configurations of the LISA-Taiji network. We find that the co-inclination configuration offers its advantages over the anti-inclination one and can achieve signal-to-noise ratios up to 17.3 for the vector modes and 10.4 for the scalar modes with the energy density spectrum as $\Omega_{GW}^p(f)=10^{-12}$. Our method can be used to measure beyond-general-relativity polarization modes of SGWBs at mHz frequency band, opening a new avenue for testing alternative gravity theories.