Testing mirror symmetry in the Universe with LIGO-Virgo black-hole mergers

Understand

Certain precessing black-hole mergers produce gravitational waves with net circular polarization, understood as an imbalance between right- and left-handed amplitudes.

• According to the Cosmological Principle, such emission must average to zero across all binary mergers in our Universe to preserve mirror-reflection symmetry at very large scales.
• We present a new independent gravitational-wave test of this hypothesis.
• Using a novel observable based on the Chern-Pontryagin pseudo-scalar, we measure the emission of net circular polarization across 47 black-hole mergers recently analyzed by Islam et.