Can one tell Einstein's unimodular theory from Einstein's general relativity?

TL;DR

This paper compares Einstein's unimodular gravity with general relativity in the quadratic regime and suggests quantum effects could distinguish between the two theories.

Contribution

It provides a broad framework for comparison and proposes that quantum effects can differentiate unimodular gravity from general relativity.

Findings

Quantum effects can, in principle, discriminate between the theories.

Unimodular gravity and general relativity are distinguishable in the quadratic regime.

The comparison is made within a broad theoretical framework.

Abstract

The so called unimodular theory of gravitation is compared with general relativity in the quadratic (Fierz-Pauli) regime, using a quite broad framework, and it is argued that quantum effects allow in principle to discriminate between both theories.