Unimodular Gravity and Averaging

TL;DR

This paper proposes a simplified scalar averaging method within unimodular gravity to better interpret inhomogeneous cosmological data, demonstrating how averaging affects the dynamics through curvature corrections.

Contribution

It introduces a novel scalar averaging approach in unimodular gravity, providing a clearer framework for understanding inhomogeneities in cosmology.

Findings

Averaging introduces curvature-like corrections to cosmological dynamics.

The approach simplifies the averaging process compared to traditional methods.

Application to a dust model illustrates the impact of averaging on evolution equations.

Abstract

The question of the averaging of inhomogeneous spacetimes in cosmology is important for the correct interpretation of cosmological data. In this paper we suggest a conceptually simpler approach to averaging in cosmology based on the averaging of scalars within unimodular gravity. As an illustration, we consider the example of an exact spherically symmetric dust model, and show that within this approach averaging introduces correlations (corrections) to the effective dynamical evolution equation in the form of a spatial curvature term.