Radiative instability of quantum electrodynamics in chiral matter

TL;DR

This paper investigates how chiral matter modifies photon and fermion stability, leading to spontaneous radiation processes, with spectra derived and polarization effects analyzed, including the influence of domain walls.

Contribution

It introduces the concept of radiative instability in QED within chiral media, deriving spectra for spontaneous radiation and pair production, and analyzing polarization and domain wall effects.

Findings

Photon and fermion states are unstable to spontaneous radiation.

Spectra depend on the sign of chiral conductivity.

Domain walls influence radiation spectra.

Abstract

Modification of the photon dispersion relation in chiral matter enables $1\to 2$ scattering. As a result, the single fermion and photon states are unstable to photon radiation and pair production respectively. In particular, a fast fermion moving through chiral matter can spontaneously radiate a photon, while a photon can spontaneously radiate a fast fermion and anti-fermion pair. The corresponding spectra are derived in the ultra-relativistic approximation. It is shown that the polarization of the produced and decayed photons is determined by the sign of the chiral conductivity. Impact of a flat thin domain wall on the spectra is computed.