Chiral anomalies induced by gravitational waves

TL;DR

This paper demonstrates that dynamical solutions to Einstein and Maxwell equations with circularly polarized radiation can induce chiral anomalies, leading to the spontaneous generation of helicity fluxes from the quantum vacuum in astrophysical contexts.

Contribution

It reveals a novel mechanism where classical gravitational and electromagnetic waves can trigger chiral anomalies without topological backgrounds.

Findings

Circularly polarized gravitational waves induce chiral anomalies.

Astrophysical systems with such radiation generate helicity fluxes.

Quantum vacuum produces helicity fluxes in these conditions.

Abstract

Chiral symmetries in field theory are typically affected by an anomaly in the quantum theory. This anomaly emerges when one introduces an interaction with a Yang-Mills or gravitational background. Physical applications of this quantum effect have been traditionally connected to topological questions of the background field and the study of instantons. We show here how one can alternatively find situations of physical interest that only involve ordinary, but dynamical solutions of the background field equations. More precisely, we show that solutions to the Einstein (Maxwell) equations are able to trigger the chiral anomaly if and only if they admit a flux of gravitational (electromagnetic) radiation with net circular polarization. As a consequence, astrophysical systems that admit such radiation spontaneously generate a flux of particles with net helicity from the quantum vacuum.