Lifetime of a massive particle in a de Sitter universe

TL;DR

This paper investigates how massive particles decay in de Sitter space-time, revealing that particles above a critical mass are unstable with velocity-independent lifetimes, while lighter particles have quantized decay products and zero lifetime.

Contribution

It provides a detailed analysis of particle decay processes in de Sitter space, highlighting mass-dependent stability and decay characteristics not present in flat space.

Findings

Particles above critical mass are unstable in de Sitter space.

Decay lifetimes are velocity-independent for certain mass ranges.

Lighter particles have quantized decay products and zero lifetime.

Abstract

We study particle decay in de Sitter space-time as given by first order perturbation theory in an interacting quantum field theory. We show that for fields with masses above a critical mass $m_c$ there is no such thing as particle stability, so that decays forbidden in flat space-time do occur there. The lifetime of such a particle also turns out to be independent of its velocity when that lifetime is comparable with de Sitter radius. Particles with lower mass are even stranger: The masses of their decay products must obey quantification rules, and their lifetime is zero.