On interactions of higher spin fields with gravity and branes in AdS_5

TL;DR

This paper constructs and analyzes higher spin fields interacting with gravity and branes in AdS_5, demonstrating conditions for unitarity and exploring implications for braneworld scenarios and dark matter.

Contribution

It develops tree-level unitary actions for higher spin fields in AdS_5 and Randall-Sundrum models, revealing constraints on bosonic higher spins and their potential as dark matter.

Findings

Higher spin interactions with gravity are tree-level unitary in AdS_5.

Bosonic higher spins interact with branes only under specific conditions.

Higher spins in Randall-Sundrum II are produced by graviton decay at trans-Planckian scales.

Abstract

We construct actions of higher spin fields interacting with gravity on AdS_5 backgrounds such that the Compton scattering amplitudes of the interaction are tree-level unitary. We then consider higher-spin fields in the Randall-Sundrum scenario. There, in the fermionic case, we construct a tree-level unitary action of higher spin fields interacting with branes and linearised gravity. In the bosonic case we show that this is not in general possible. A tree-level unitary action of bosonic higher spins interacting with linearised gravity and branes is only possible in the following cases: The brane is a pure tension brane and/or Dirichlet boundary conditions are imposed thereby making bosonic higher spin fields invisible to a brane observer. We finally show that higher spins in Randall-Sundrum II braneworlds can only be produced by (decay into) gravitons at trans-Planckian scales. We end by commenting on the possible relevance of higher-spin unparticles as Dark Matter candidates.