Self-Protection of Massive Cosmological Gravitons

TL;DR

This paper investigates the stability of massive cosmological gravitons, revealing they are self-protected against unitarity violations through strong coupling effects in expanding universe models.

Contribution

It provides a detailed analysis of the classical and quantum stability of massive gravitons in cosmological settings, highlighting a self-protection mechanism against unitarity issues.

Findings

Massive gravitons are stable on de Sitter backgrounds.

Self-protection occurs via strong coupling phenomena.

Unitarity violations are avoided in expanding universes.

Abstract

Relevant deformations of gravity present an exciting window of opportunity to probe the rigidity of gravity on cosmological scales. For a single-graviton theory, the leading relevant deformation constitutes a graviton mass term. In this paper, we investigate the classical and quantum stability of massive cosmological gravitons on generic Friedman backgrounds. For a Universe expanding towards a de Sitter epoch, we find that massive cosmological gravitons are self-protected against unitarity violations by a strong coupling phenomenon.