On the Decay of Massive Fields in de Sitter

TL;DR

This paper investigates the decay of massive scalar fields in de Sitter space, revealing their instability and computing decay rates through loop calculations, with implications for quantum field behavior in curved spacetime.

Contribution

It provides the first detailed computation of decay rates for massive fields in de Sitter space using 1-loop and Schwinger-Dyson resummation techniques.

Findings

Decay rate is exponentially suppressed for large mass-to-Hubble ratio

Decay process is absent in flat spacetime, highlighting de Sitter-specific effects

Resummation methods confirm the stability behavior at different mass scales

Abstract

Interacting massive fields with m > d H/2 in d+1 dimensional de Sitter space are fundamentally unstable. Scalar fields in this mass range can decay to themselves. This process (which is kinematically forbidden in Minkowski space) can lead to an important change to the propagator and the physics of these fields. We compute this decay rate by doing a 1-loop computation for a massive scalar field with a cubic interaction. We resum the 1-loop result by consistently solving the Schwinger-Dyson equations. We also perform an explicit resummation of all chain graphs in the case of the retarded propagator. The decay rate is exponentially suppressed for large m/H and the flat space answer (vanishing decay rate) is reproduced in that limit.