Radiation of inertial scalar particles in the de Sitter universe

TL;DR

This paper studies how inertial scalar particles radiate in a de Sitter universe, revealing that soft-photon emission dominates and inertial particles lose momentum similarly to decelerated particles in flat spacetime.

Contribution

It provides a detailed analysis of scalar QED radiation processes in de Sitter space, highlighting the dominance of soft-photon emission and momentum loss of inertial particles.

Findings

Soft-photon emission dominates the radiation process.

Inertial particles in de Sitter space lose momentum.

Radiation pattern qualitatively similar to Minkowski space.

Abstract

We investigate the radiation from an inertial scalar particle evolving in a de Sitter expanding Universe. In the context of scalar QED the process is generated by the first order term in the perturbation theory expansion of the S-matrix. The partial transition probability is obtained and analysed, and soft-photon emission is found to dominate overall. It has been argued that an inertial particle evolving in dS spacetime loses physical momentum just as a decelerated particle in Minkowski space does. It is thus expected that an inertial charge will radiate in a similar way. We investigate the radiated energy and make a qualitative comparison of the angular distribution of the energy with the radiation pattern in the latter case.