Cosmological mirror symmetry and gravitational-wave helicity

TL;DR

This paper proposes a novel method using gravitational-wave circular polarization to test the universe's mirror symmetry, revealing a correlation with black hole helicity and offering a new observational approach in cosmology.

Contribution

It introduces a new geometric observable in general relativity to measure circular polarization, enabling an observer-independent test of cosmological mirror symmetry.

Findings

Circular polarization correlates with black hole helicity.

Current LIGO-Virgo data provides initial constraints.

Future detections will improve the test's sensitivity.

Abstract

Our current understanding of the Universe relies on the hypothesis that, when observed at sufficiently large scales, it looks statistically identical regardless of location or direction of observation. Consequently, the Universe should exhibit mirror-reflection symmetry. In this essay, we show that gravitational-wave astronomy provides a unique, observer-independent test of this hypothesis. In particular, we analyze the average circular polarization emitted by an ensemble of binary black hole mergers detected by LIGO-Virgo, which we compute using a novel geometric and chiral observable in general relativity. We discuss current results and future prospects with upcoming detections and technical advancements. Moreover, we show that this circular polarization and the helicity of the remnant black hole are linearly correlated, drawing a conceptual parallel with Wu experiment in particle physics.