Chiral Anomalous Dispersion

TL;DR

This paper investigates how chiral media induce helicity-dependent anomalous dispersion in graviton and electromagnetic wave propagation, revealing negative group velocities and extending the phenomenon across different fields.

Contribution

It demonstrates that chiral media cause helicity-dependent anomalous dispersion in polarized wave propagation, a novel effect in both gravitational and electromagnetic contexts.

Findings

Circularly polarized metric perturbations exhibit helicity-dependent group velocities.

Negative group velocities can occur, indicating anomalous dispersion.

The phenomenon extends to electromagnetic waves in chiral plasmas.

Abstract

The linearized Einstein equation describing graviton propagation through a chiral medium appears to be helicity dependent. We analyze features of the corresponding spectrum in a collision-less regime above a flat background. In the long wave-length limit, circularly polarized metric perturbations travel with a helicity dependent group velocity that can turn negative giving rise to a new type of an anomalous dispersion. We further show that this chiral anomalous dispersion is a general feature of polarized modes propagating through chiral plasmas extending our result to the electromagnetic sector.