Variation of the speed of light with temperature of the expanding universe

TL;DR

This paper explores a model where the speed of light varies with the universe's temperature, suggesting it was much higher in the early universe but decreases significantly before inflation, challenging the varying speed of light hypothesis.

Contribution

It introduces an extended relativistic dynamics framework that explicitly relates the speed of light to the universe's temperature without violating special relativity.

Findings

Speed of light was much larger in the early universe

Speed of light decreased drastically before inflation

Varying speed of light may not solve the horizon problem

Abstract

From an extended relativistic dynamics for a particle moving in a cosmic background field with temperature T, we aim to obtain the speed of light with an explicit dependence on the background temperature of the universe. Although finding the speed of light in the early universe much larger than its current value, our approach does not violate the postulate of special relativity. Moreover, it is shown that the high value of the speed of light in the early universe was drastically decreased before the beginning of the inflationary period. So we are led to conclude that the theory of varying speed of light should be questioned as a possible solution of the horizon problem.