Varying c cosmology and Planck value constraints

TL;DR

This paper examines models with varying speed of light to address cosmological problems, finding limited effectiveness and issues with quantum dominance in such scenarios.

Contribution

It critically analyzes the viability of varying c cosmologies in solving standard big bang problems, highlighting constraints related to Planck scales.

Findings

Higher c models have limited ability to resolve cosmological problems.

Constantly decreasing c leads to quantum dominance at late times.

Varying c models face significant theoretical constraints.

Abstract

It has been suggested that by increasing the speed of light during the early universe various cosmological problems of standard big bang cosmology can be overcome, without requiring an inflationary phase. However, we find that as the Planck length and Planck time are then made correspondingly smaller, and together with the need that the universe should not re-enter a Planck epoch, the higher $c$ models have very limited ability to resolve such problems. For a constantly decreasing $c$ the universe will quickly becomes quantum gravitationally dominated as time increases: the opposite to standard cosmology where quantum behaviour is only ascribed to early times.