Translating current ALP photon coupling strength bounds to the Randall-Sundrum model

TL;DR

This paper translates existing bounds on ALP-photon coupling into constraints on the size of the extra dimension in the Randall-Sundrum model, revealing limitations for light ALPs in addressing the hierarchy problem.

Contribution

It relates ALP coupling bounds to the RS model's extra dimension size, providing new constraints relevant for hierarchy problem considerations.

Findings

Current bounds imply a minimum ALP mass of ~0.1 GeV for hierarchy problem relevance.

Constraints do not resolve the gauge hierarchy problem for ultralight ALPs.

Massive ALPs are required to impact the hierarchy problem within the RS framework.

Abstract

In this article, we look at the current bounds on the coupling strength of axion-like particles (ALPs) with two photons in the context of the Randall-Sundrum (RS) model. We relate the coupling strength to the compactification radius that governs the size of the extra dimension in the RS warped geometry model and show how the current bounds on the ALP can be used to derive appropriate constraints on the size of the extra fifth dimension in the RS model. We show that the resulting constraints fail to resolve the gauge hierarchy problem for light/ultralight ALPs and require a massive ALP of at least $m_{a} \gtrsim 0.1$ [GeV] to be relevant in the context of the hierarchy problem when the gauge field is in the bulk.