An interpretation of the acceleration of the universe's expansion

TL;DR

This paper proposes a novel matter-based explanation for the universe's accelerated expansion, suggesting that matter with negative pressure at low densities can drive acceleration without dark energy, aligning with supernova data.

Contribution

It introduces a new matter equation of state derived from statistical mechanics, offering an alternative to dark energy for explaining cosmic acceleration.

Findings

Matter can have negative pressure at low densities.

The model predicts a universe dominated by a nearly constant energy density.

Supernova data cannot distinguish this model from the standard LCDM model.

Abstract

We have observed the acceleration of the expansion of the universe. To explain this phenomenon, we usually introduce the dark energy (DE) which has a negative pressure or we need to modify the Einstein's equation to produce a term which is equivalent to the dark energy. Are there other possibilities? Combining our previous works of statistical mechanics of self-gravitating system with the derivation of van der waals equation, we propose a different matter's equation of state (EoS) in this paper. Then we find that if the matter's density is low enough, its pressure can be negative, which means that it is the matter that drives the expansion's acceleration. So here we will not need to add the DE to the universe. Our results also predict that the universe finally tends to be dominated by an approximate constant energy density, but its value can be smaller than DE. The data of Supernova can not differentiate our model from the standard model, but they may indicate some deviations from LCDM.