Cosmic Acceleration Caused by the Extra-Dimensional Evolution in a Generalized Randall-Sundrum Model

TL;DR

This paper proposes a generalized Randall-Sundrum model with anisotropic metrics that naturally explains the universe's acceleration through extra-dimensional evolution, avoiding fine-tuning and dark energy assumptions.

Contribution

It introduces a new higher-dimensional model with positive brane tensions and stable configurations that accounts for cosmic acceleration without fine-tuning or dark energy.

Findings

Achieves a tiny positive effective cosmological constant without fine tuning.

Demonstrates universe acceleration due to extra-dimensional evolution.

Ensures stability with positive brane tensions.

Abstract

We investigate a $(n+1)$-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors. One obtain a positive effective cosmological constant $\Omega_{eff}\sim10^{-124}$ (in Planck unit) which only need a solution $kr\simeq50-80$ without fine tuning, and both the visible and hidden brane tensions are positive which results in the two branes to be stable. Then, we find that the Hubble parameter is seem to be a constant in a large region near its minimum, thus causing the acceleration of the universe. Therefore, the fine tuning problem also can be solved in this model. Meanwhile, the scale of extra dimensions is smaller than the observed scale but greater than the Planck length. This demonstrates that the observed present acceleration of the universe is caused by the extra-dimensional evolution rather than dark energy.