Weyl transverse gravity (WTDiff) and the cosmological constant

TL;DR

This paper introduces scale-invariant transverse gravitational theories that are invariant under specific metric rescalings and a subset of diffeomorphisms, providing a framework where the cosmological constant is naturally forbidden.

Contribution

The paper presents a novel class of scale-invariant transverse gravitational theories that restrict diffeomorphism invariance, offering a new approach to addressing the cosmological constant problem.

Findings

Theories are invariant under pure metric rescalings.

They are invariant under transverse diffeomorphisms.

Theories forbid the presence of a cosmological constant.

Abstract

Scale invariant (transverse) gravitational theories are introduced. They are invariant under pure metric rescalings (i.e. the matter fields are inert under those). This symmetry forbids the presence of a cosmological constant. Those theories are not invariant under the full set of diffeomorphisms, but only with respect to those locally characterized by the fact that their generator is transverse $\pd_\a \xi^\a=0$.