Mass loss by a scalar charge in an expanding universe

TL;DR

This paper investigates how a scalar charge in expanding universes, like de Sitter and matter-dominated spacetimes, loses and regains mass due to scalar radiation emission, revealing universe-dependent mass evolution behaviors.

Contribution

It provides the first analysis of scalar charge mass loss in expanding cosmological backgrounds, showing different mass evolution dynamics in de Sitter and matter-dominated universes.

Findings

In de Sitter space, the particle radiates all its mass in finite time.

In matter-dominated universe, mass loss depends on charge size, with possible mass recovery.

Scalar radiation causes non-constant mass evolution in expanding universes.

Abstract

We study the phenomenon of mass loss by a scalar charge -- a point particle that acts a source for a noninteracting scalar field -- in an expanding universe. The charge is placed on comoving world lines of two cosmological spacetimes: a de Sitter universe, and a spatially-flat, matter-dominated universe. In both cases, we find that the particle's rest mass is not a constant, but that it changes in response to the emission of monopole scalar radiation by the particle. In de Sitter spacetime, the particle radiates all of its mass within a finite proper time. In the matter-dominated cosmology, this happens only if the charge of the particle is sufficiently large; for smaller charges the particle first loses some of its mass, but then regains it all eventually.