Novel nonlinear kinetic terms for gravitons

TL;DR

This paper introduces new derivative terms for spin-2 fields in bi-gravity, showing they can eliminate ghosts and relate to Weyl and New Massive Gravity, with implications for UV scales and higher derivatives.

Contribution

It proposes novel derivative terms for gravitons and demonstrates their potential to produce ghost-free bi-gravity models, connecting to known gravity theories.

Findings

Identification of bi-gravity models with ghost-free properties

Connection of Weyl and New Massive Gravity to novel derivative terms

Analysis of UV cut-off scales and higher-derivative effects

Abstract

A set of novel derivative terms for spin-2 fields are proposed. They are the wedge products of curvature two-forms and vielbeins. In this work, we investigate the properties of novel two-derivative terms in the context of bi-gravity. Based on a minisuperspace analysis, we identify a large class of bi-gravity models where the Boulware-Deser ghost could be absent. We give a new perspective that Weyl Gravity and New Massive Gravity belong to this class of bi-gravity models involving novel derivative terms. In addition, we discuss the UV cut-off scales, dynamical symmetric conditions and novel higher-derivative terms.