Regge growth of isolated massive spin-2 particles and the Swampland

TL;DR

This paper demonstrates that theories with an isolated massive spin-2 particle coupled to gravity exhibit super-$s^2$ growth in scattering amplitudes, supporting the Swampland conjecture that such theories are inconsistent with quantum gravity.

Contribution

It proves that all effective theories with a single massive spin-2 particle and finite derivatives have amplitudes growing faster than $s^2$, indicating they belong to the Swampland.

Findings

Scattering amplitudes grow faster than $s^2$ in these theories.

Supports the Swampland conjecture for massive spin-2 particles.

Provides constraints on effective theories with massive spin-2 fields.

Abstract

We consider an effective theory with a single massive spin-2 particle and a gap to the cutoff. We couple the spin-2 particle to gravity, and to other lower-spin fields, and study the growth of scattering amplitudes of the particle in the Regge regime: where $s$ is much larger than $t$ and also any mass scales in the effective theory, but still much lower than the cutoff scale of the theory and therefore any further massive spin-2 particles. We include in the effective theory all possible operators, with an arbitrary, but finite, number of derivatives. We prove that the scattering amplitude grows strictly faster than $s^2$ in any such theory. Such fast growth goes against expected bounds on Regge growth. We therefore find further evidence for the Swampland spin-2 conjecture: that a theory with an isolated massive spin-2 particle, coupled to gravity, is in the Swampland.