Parity-breaking galaxy 4-point function from lensing by chiral gravitational waves

TL;DR

This paper investigates whether lensing by a chiral gravitational-wave background can produce a detectable parity-breaking galaxy four-point correlation, finding it unlikely with current surveys but potentially observable with future 21cm observations.

Contribution

It introduces a novel mechanism linking chiral gravitational waves to parity-breaking galaxy correlations, providing estimates of detectability.

Findings

Current galaxy surveys are unlikely to detect the signal.

Future 21cm observations may have sufficient sensitivity.

The proposed mechanism connects gravitational wave chirality to galaxy correlation signals.

Abstract

Recent searches for parity breaking in the galaxy four-point correlation function, as well as the prospects for greatly improved sensitivity to parity breaking in forthcoming surveys, motivate the search for physical mechanisms that could produce such a signal. Here we show that a parity-violating galaxy four-point correlation function may be induced by lensing by a chiral gravitational-wave background. We estimate the amplitude of a signal that would be detectable with a current galaxy survey, taking into account constraints to the primordial gravitational-wave-background amplitude. We find that this mechanism is unlikely to produce a signal large enough to be seen with a galaxy survey but note that it may come within reach with future 21cm observations.