Quantum Larmor radiation in de Sitter spacetime

TL;DR

This paper investigates quantum Larmor radiation emitted by an inertial charge in de Sitter spacetime, revealing classical and quantum effects, including a negative quantum correction and divergence at high frequencies.

Contribution

It provides a perturbative scalar QED calculation of radiation in de Sitter space, highlighting quantum corrections and divergences linked to spacetime properties.

Findings

Classical Larmor formula is recovered in the non-relativistic limit.

Quantum correction to radiation energy is negative.

Ultra-relativistic case shows logarithmic divergence at high frequencies.

Abstract

We study the radiation emitted by inertial charge evolving on the expanding de Sitter spacetime. Performing a perturbative calculation, within scalar quantum electrodynamics (sQED), we obtain the transition amplitude for the process and using this we define the energy radiated by the source. In the non-relativistic limit we find that the leading term is compatible with the classical result (Larmor formula). The first quantum correction is found to be negative, a result which is in line with a number of similar quantum field theory results. For the ultra-relativistic case we find a logarithmic divergence of the emitted energy for large frequencies, which we link to the nature of the spacetime. We compare our results with that of Nomura et al. (2006), where the authors make a similar calculation for a general conformally flat spacetime.