Variable-Speed-of-Light Cosmology from Brane World Scenario

TL;DR

This paper proposes a variable-speed-of-light cosmology within a brane world framework, suggesting gravitons can travel faster than photons and addressing key cosmological problems through radion dynamics and inflation.

Contribution

It introduces a bimetric brane world model where graviton speed varies, offering solutions to flatness and cosmological constant problems not present in standard models.

Findings

Graviton speed decreases to current value rapidly.

Radion field can drive inflation under slow-roll conditions.

Model addresses flatness and cosmological constant issues.

Abstract

We argue that the four-dimensional universe on the TeV brane of the Randall-Sundrum scenario takes the bimetric structure of Clayton and Moffat, with gravitons traveling faster than photons instead, while the radion varies with time. We show that such brane world bimetric model can thereby solve the flatness and the cosmological constant problems, provided the speed of a graviton decreases to the present day value rapidly enough. The resolution of other cosmological problems such as the horizon problem and the monopole problem requires supplementation by inflation, which may be achieved by the radion field provided the radion potential satisfies the slow-roll approximation.