Accelerating Universe as Window for Extra Dimensions

TL;DR

This paper explores five-dimensional cosmological models where extra dimensions induce negative pressure, potentially explaining the universe's acceleration without dark energy, and suggests that such acceleration indicates the presence of extra spatial dimensions.

Contribution

It introduces new five-dimensional solutions with equations of state that produce accelerated expansion, linking higher-dimensional gravity to observable cosmic acceleration without dark energy.

Findings

Higher-dimensional metric terms generate effective negative pressure.

Solutions show transition from deceleration to acceleration.

Models mimic quintessence with Chaplygin-type fluid.

Abstract

Homogeneous cosmological solutions are obtained in five dimensional space time assuming equations of state $ p = k\rho $ and $ p_{5}= \gamma\rho$ where p is the isotropic 3 - pressure and $p_{5}$, that for the fifth dimension. Using different values for the constants k and $\gamma$ many known solutions are rediscovered. Further the current acceleration of the universe has led us to investigate higher dimensional gravity theory, which is able to explain acceleration from a theoretical view point without the need of introducing dark energy by hand. We argue that the terms containing higher dimensional metric coefficients produce an extra negative pressure that apparently drives an acceleration of the 3D space, tempting us to suggest that the accelerating universe seems to act as a window to the existence of extra spatial dimensions. Interestingly the 5D matter field remains regular while the \emph{effective} negative pressure is responsible for the inflation. Relaxing the assumptions of two equations of state we also present a class of solutions which provide early deceleration followed by a late acceleration in a unified manner. Interesting to point out that in this case our cosmology apparently mimics the well known quintessence scenario fuelled by a generalised Chaplygin-type of fluid where a smooth transition from a dust dominated model to a de Sitter like one takes place.