Cyclic universe from uniform rate inflation on the brane with a timelike extra dimension

TL;DR

This paper presents a non-singular cyclic universe model with uniform-rate inflation on an anisotropic brane, incorporating a timelike extra dimension that stabilizes the bounce and aligns with observational data.

Contribution

It introduces a novel anisotropic braneworld scenario with uniform-rate inflation, resolving the initial singularity and demonstrating observational viability without fine-tuning.

Findings

Achieves a non-singular cyclic universe with smooth bounces.

Shows that anisotropic shear is suppressed near the bounce.

Demonstrates consistency with observational data across different anisotropy levels.

Abstract

We investigate a non-singular cosmological scenario in which uniform-rate inflation is realised on an anisotropic Shtanov-Sahni braneworld. The model naturally resolves the initial singularity resulting in an infinite number of smooth non-singular bounces, while accommodating a phase of accelerated expansion driven by a scalar field rolling at a constant rate. The presence of a timelike extra dimension induces high-energy corrections to the effective Friedmann dynamics, allowing anisotropic shear to be dynamically suppressed near the bounce and rendering the background evolution stable. We derive the full background dynamics analytically and demonstrate that uniform-rate inflation can be consistently embedded within an anisotropic braneworld framework. Primordial scalar and tensor perturbations are analysed using the $\delta N$ formalism, ensuring that only physically relevant modes exiting the horizon during inflation contribute to observable quantities. Remarkably, we find that observational consistency can be achieved with different levels of anisotropy in the two different scenarios we consider, without compromising the smoothness or stability of the bounce. Our results establish uniform-rate inflation on an anisotropic braneworld as a robust and observationally viable alternative to standard inflationary cosmology, offering a compelling framework in which non-singular early-universe dynamics and precision cosmology can be consistently unified.