Unimodular quantum gravity and the cosmological constant

TL;DR

This paper demonstrates that unimodular gravity's one-loop effective action aligns with that of ordinary gravity, with differences in handling the cosmological constant, suggesting a potential resolution to the cosmological constant problem.

Contribution

It shows that unimodular gravity naturally decouples vacuum energy from gravity, offering a novel approach to the cosmological constant problem.

Findings

Vacuum energy does not gravitate in unimodular gravity.

The effective actions of unimodular and ordinary gravity are equivalent except for global scale treatment.

Unimodular gravity provides a new perspective on the cosmological constant issue.

Abstract

It is shown that the one-loop effective action of unimodular gravity is the same as that of ordinary gravity, restricted to unimodular metrics. The only difference is in the treatment of the global scale degree of freedom and of the cosmological term. A constant vacuum energy does not gravitate, addressing one aspect of the cosmological constant problem.