Detecting Parity-Violating Gravitational Wave Backgrounds with Pulsar Polarization Arrays

TL;DR

This paper explores how pulsar polarization arrays can detect parity-violating gravitational wave backgrounds by analyzing polarization rotation and cross-correlations, offering a new method complementary to existing techniques.

Contribution

It introduces a geometric optics framework to evaluate pulsar polarimetry's sensitivity to circular polarization in stochastic GW backgrounds, highlighting its potential for future observations.

Findings

Cross-correlation between pulsar timing and polarimetry isolates circular polarization.

Polarization rotation induced by GWs can be modeled using geometric optics.

Future facilities like SKA could detect GW circular polarization with sensitivities comparable to astrometric methods.

Abstract

Pulsar timing arrays probe isotropic stochastic gravitational wave (GW) backgrounds in the nanohertz band but are insensitive to its parity-violating component. Motivated by recent progress in pulsar polarization arrays, we study the response of pulsar polarimetry to GWs and evaluate its potential to detect circular polarization in isotropic stochastic GW backgrounds, which characterizes parity violation. Based on geometric optics, we derive the rotation of the polarization of electromagnetic waves induced by propagation through a GW background. We show that the cross-correlation between pulsar timing and polarimetry signals isolates the circular polarization component from the GW intensity, sharing the same Hellings-Downs angular pattern. With future facilities such as the SKA, timing-polarimetry correlations could reach sensitivities to the circular polarization of GWs comparable to those of the current astrometric methods.