Accelerated expansion without dark energy

TL;DR

This paper explores an alternative explanation for cosmic acceleration, suggesting that imperfect cold dark matter with negative bulk pressure, possibly due to dissipative processes, can account for the observed acceleration without dark energy.

Contribution

It introduces a model where imperfect cold dark matter with negative bulk pressure drives cosmic acceleration, challenging the necessity of dark energy in explaining observations.

Findings

Imperfect CDM with negative bulk pressure can fit observational data.

Dissipative processes during structure formation may cause effective forces leading to acceleration.

The model links cosmic acceleration to inhomogeneity formation processes.

Abstract

The fact that the LambdaCDM model fits the observations does not necessarily imply the physical existence of `dark energy'. Dropping the assumption that cold dark matter (CDM) is a perfect fluid opens the possibility to fit the data without dark energy. For imperfect CDM, negative bulk pressure is favoured by thermodynamical arguments and might drive the cosmic acceleration. The coincidence between the onset of accelerated expansion and the epoch of structure formation at large scales might suggest that the two phenomena are linked. A specific example is considered in which effective (anti-frictional) forces, which may be due to dissipative processes during the formation of inhomogeneities, give rise to accelerated expansion of a CDM universe.