Spectral Representation and the Averaging Problem in Cosmology

TL;DR

This paper introduces a spectral distance framework to address the cosmological averaging problem, proposing a new metric space approach for analyzing spacetime and universe evolution.

Contribution

It develops a spectral distance measure and a corresponding space of all spaces, providing a novel mathematical framework for the averaging problem in cosmology.

Findings

Spectral distance effectively measures closeness between different spaces.

The spectral framework facilitates model fitting and dynamical analysis in cosmology.

The approach supports the concept of scale-dependent universe evolution.

Abstract

We investigate the averaging problem in cosmology as the problem of introducing a distance between spaces. We first introduce the spectral distance, which is a measure of closeness between spaces defined in terms of the spectra of the Laplacian. Then we define a space S, the space of all spaces equipped with the spectral distance. We argue that this space S can be regarded as a metric space and that it also possess other desirable properties. These facts make the space S a suitable arena for spacetime physics. We apply the spectral framework to the averaging problem: We sketch the model-fitting procedure in terms of the spectral representation, and also discuss briefly how to analyze the dynamical aspects of the averaging procedure with this scheme. In these analyses, we are naturally led to the concept of the apparatus- and the scale-dependent effective evolution of the universe. These observations suggest that the spectral scheme seems to be suitable for the quantitative analysis of the averaging problem in cosmology.