Perturbations to the Cosmological Expansion in a Grainy Universe

TL;DR

This paper explores how small-scale inhomogeneities, modeled as discrete grains instead of a fluid, could influence the overall expansion of the Universe, potentially leading to observable perturbations.

Contribution

It introduces a novel perspective by analyzing the impact of granular matter distribution on cosmological expansion, contrasting with the traditional fluid approximation.

Findings

Small-scale inhomogeneities can cause measurable perturbations in cosmic expansion.

Granular matter distribution may lead to deviations from standard cosmological models.

Potential implications for interpreting large-scale structure observations.

Abstract

The matter content of the Universe is generally regarded as a perfect fluid on sufficiently large scales, for all epochs. But the recent cosmological matter distribution, consisting of an (ideally) random distribution of gravitationally collapsed structures, is more accurately described as a collection of discrete grains, than as a fluid. It is well known that granular materials may have very different macroscopic properties than fluids; analogously, we investigate the possibility that pervasive small-scale inhomogeneities in the recent Universe may lead to perturbations of the cosmological expansion on intermediate and/or large scales.