Stability of Massive Cosmological Gravitons

TL;DR

This paper investigates the stability conditions of massive spin-2 fields in (A)dS spacetimes, establishing the mass threshold for stability and describing the properties of the partially massless theory.

Contribution

It provides a detailed analysis of the stability of massive gravitons in (A)dS backgrounds and characterizes the partially massless limit with four propagating degrees of freedom.

Findings

Stable for m^2 >= 2Λ/3 with positive energy

Unstable for m^2 < 2Λ/3 due to helicity 0 energy

Partially massless theory at m^2=2Λ/3 has 4 degrees of freedom

Abstract

We analyze the physics of massive spin 2 fields in (A)dS backgrounds and exhibit that: The theory is stable only for masses m^2 >= 2\Lambda/3, where the conserved energy associated with the background timelike Killing vector is positive, while the instability for m^2<2\Lambda/3 is traceable to the helicity 0 energy. The stable, unitary, partially massless theory at m^2=2\Lambda/3 describes 4 propagating degrees of freedom, corresponding to helicities (+/-2,+/-1) but contains no 0 helicity excitation.