Axions And Self-Interacting Dark Matter In The Heterotic String-Derived Model

TL;DR

This paper revisits a heterotic string-derived model, finding that its axions cannot solve the strong CP problem and exploring the natural presence of self-interacting dark matter within the hidden sector's non-Abelian gauge group.

Contribution

It demonstrates that the model's axions are unsuitable for solving the strong CP problem and identifies the natural emergence of self-interacting dark matter in the hidden sector.

Findings

Two axions are either harmful or massive, preventing them from solving the strong CP problem.

The model naturally includes four copies of a hidden SU(2) gauge group, supporting self-interacting dark matter.

The results align with previous findings on axion limitations in similar models.

Abstract

After revisiting the heterotic string-derived low-energy effective model of \cite{Ashfaque:2016ydg, Athanasopoulos:2014bba, Faraggi:2016xnm, Ashfaque:2016jha} constructed in the four-dimensional free fermionic formulation, we find two axions which are either harmful or massive. As a direct consequence, they can not solve the strong $CP$ problem which is in complete agreement with \cite{Lopez:1990iq, Halyo:1993xn}. We also explore the possibility of the self-interacting dark matter residing in the non-Abelian gauge group present in the hidden sector \cite{Faraggi:2000pv}. We find that the low-energy string-derived model naturally welcomes the self-interacting dark matter as $4$ copies of the non-Abelian, hidden $SU(2)$ gauge group factor are present.