Interactions for a collection of spin-two fields intermediated by a massless p-form

TL;DR

This paper explores possible interactions between multiple spin-two fields and a massless p-form, revealing a new PT-breaking coupling in specific dimensions but showing no viable cross-interactions among different gravitons.

Contribution

It identifies a novel class of couplings in D=p+2 dimensions that break PT-invariance, expanding understanding of spin-two field interactions.

Findings

Standard interactions align with General Relativity

New PT-breaking couplings exist in specific dimensions

No consistent cross-interactions among different gravitons

Abstract

Under the general hypotheses of locality, smoothness of interactions in the coupling constant, Poincare invariance, Lorentz covariance, and preservation of the number of derivatives on each field, we investigate the cross-couplings of one or several spin-two fields to a massless p-form. Two complementary cases arise. The first case is related to the standard interactions from General Relativity, but the second case describes a new, special type of couplings in D=p+2 spacetime dimensions, which break the PT-invariance. Nevertheless, no consistent, indirect cross-interactions among different gravitons with a positively defined metric in internal space can be constructed.