Extension of unimodular gravity and the cosmological constant

TL;DR

This paper proposes a novel approach to cancel the cosmological constant by using the metric determinant as a self-adjusting field, restricting coordinate transformations, and demonstrating natural cancellation in cosmology with quantum effects.

Contribution

It introduces a new method involving the metric determinant as a self-adjusting q-field, extending unimodular gravity without fine-tuning, and explores its cosmological implications.

Findings

Natural cancellation of initial cosmological constant with quantum effects

Restricted coordinate transformations to unit Jacobian

Cosmological models show self-adjustment mechanism

Abstract

A new way is proposed to cancel the cosmological constant. The proposal involves the metric determinant acting as a type of self-adjusting $q$-field without need of a fine-tuned chemical potential. Since the determinant of the metric now plays a role in the physics, the allowed coordinate transformations are restricted to those with unit Jacobian. This approach to the cosmological constant problem is, therefore, similar to the unimodular-gravity approach of the previous literature. The resulting cosmology has been studied and the obtained results show the natural cancellation of an initial cosmological constant if quantum-dissipative effects are included.