Semiclassical Unimodular Gravity

Understand

Classically, unimodular gravity is known to be equivalent to General Relativity (GR), except for the fact that the effective cosmological constant $\Lambda$ has the status of an integration constant.

• Here, we explore various formulations of unimodular gravity beyond the classical limit.
• We first consider the non-generally covariant action formulation in which the determinant of the metric is held fixed to unity.
• We argue that the corresponding quantum theory is also equivalent to General Relativity for localized perturbative processes which take place in generic backgrounds of infinite volume (such as asymptotically flat spacetimes).