Axion model in extra dimensions with TeV scale gravity

TL;DR

This paper proposes a novel axion model within large extra dimensions with TeV-scale gravity, where the axion's properties and interactions are significantly altered, affecting cosmology and astrophysics.

Contribution

It introduces a new axion model in large extra dimensions with a brane-localized axion, addressing cosmological constraints through the fat brane concept.

Findings

Model is consistent with cosmological constraints for certain dimensions

Axion Kaluza-Klein modes have enhanced interactions

The fat brane structure relaxes severe cosmological constraints

Abstract

A simple axion model is proposed in the scenario of large extra dimensions where gravity scale is as low as 1 TeV. To obtain an intermediate-scale decay constant of the axion, the axion is assumed to live in a sub-spacetime (brane) of the whole bulk. In this model there appear Kaluza-Klein modes of the axion which have stronger interaction than those of the graviton. The axion brane plays a role of absorber of the graviton Kaluza-Klein modes. Because of these reasons phenomenology and cosmology of the axion become highly non-trivial. We discuss various cosmological constraints as well as astrophysical ones and show that the model is viable for certain choices of the dimensionality of the axion brane. The structure of the model proposed here provides a viable realization of the fat brane idea to relax otherwise very severe cosmological constraints.