An expanding 4D universe in a 5D Kaluza-Klein cosmology with higher dimensional matter

TL;DR

This paper explores a 5D Kaluza-Klein cosmological model where the universe's expansion is influenced by higher-dimensional matter and dark pressure, potentially explaining late-time acceleration without dark energy.

Contribution

It introduces a 5D cosmological framework with higher-dimensional matter and dark pressure, showing how these factors can drive universe expansion and acceleration.

Findings

Higher-dimensional matter affects 4D universe dynamics.

Dark pressure influences cosmic acceleration.

Expansion may be governed by higher-dimensional equations of state.

Abstract

In the framework of Kaluza-Klein theory, we investigate a $(4+1)$-dimensional universe consisting of a $(4+1)$ dimensional Robertson-Walker type metric coupled with a $(4+1)$ dimensional energy-momentum tensor. The matter part consists of an energy density together with a pressure subject to 4D part of the $(4+1)$ dimensional energy-momentum tensor. The dark part consists of just a dark pressure $\bar{p}$, corresponding to the extra-dimension endowed by a scalar field, with no element of dark energy. It is shown that the reduced Einstein field equations are free of 4D pressure and are just affected by an effective pressure produced by the 4D energy density and dark pressure. It is then proposed that the expansion of the universe may be controlled by the equation of state in higher dimension rather than four dimensions. This may account for the emergence of unexpected current acceleration in the middle of matter dominant era.