Unusual Features of Varying Speed of Light Cosmologies

TL;DR

This paper compares simple varying speed of light cosmologies with inflationary models, highlighting new features and challenges such as explaining isotropy, horizon problems, and potential self-reproduction, providing benchmarks for future theories.

Contribution

It introduces new features of VSL cosmologies, discusses their limitations, and proposes potential self-reproduction mechanisms, advancing understanding beyond prior models.

Findings

VSL cosmologies face problems explaining isotropy.

Rapid c fall can lead to super-horizon growth of particles and black holes.

New benchmarks are proposed for testing sophisticated VSL theories.

Abstract

We contrast features of simple varying speed of light (VSL) cosmologies with inflationary universe models. We present new features of VSL cosmologies and show that they face problems explaining the cosmological isotropy problem. We also find that if c falls fast enough to solve the flatness and horizon problems then the quantum wavelengths of massive particle states and the radii of primordial black holes can grow to exceed the scale of the particle horizon. This may provide VSL cosmologies with a self-reproduction property. The constraint of entropy increase is also discussed. The new problems described in the this letter provide a set of bench tests for more sophisticated VSL theories to pass.