Constraining the Randall-Sundrum modulus in the light of recent PVLAS data

TL;DR

This paper uses recent PVLAS data to constrain the modulus parameter in Randall-Sundrum models, linking experimental limits on axion-photon coupling to extra-dimensional geometry and the gauge hierarchy problem.

Contribution

It provides bounds on the RS modulus parameter based on PVLAS constraints, connecting experimental data with string-inspired extra-dimensional models.

Findings

RS modulus constrained by PVLAS data for axion mass ≥ 0.3 eV

Bounds depend on birefringence and dichroism measurements

Implications for extra-dimensional theories and axion physics

Abstract

Recent PVLAS data put stringent constraints on the measurement of birefringence and dichroism of electromagnetic waves travelling in a constant and homogeneous magnetic field. There have been theoretical predictions in favour of such phenomena when appropriate axion-electromagnetic coupling is assumed. Origin of such a coupling can be traced in a low energy string action from the requirement of quantum consistency. The resulting couplings in such models are an artifact of the compactification of the extra dimensions present inevitably in a string scenario. The moduli parameters which encode the compact manifold therefore play a crucial role in determining the axion-photon coupling. In this work we examine the possible bounds on the value of compact modulus that emerge from the experimental limits on the coupling obtained from the PVLAS data. In particular we focus into the Randall-Sundrum (RS) type of warped geometry model whose modulus parameter is already restricted from the requirement of the resolution of gauge hierarchy problem in connection with the mass of the Higgs. We explore the bound on the modulus for a wide range of the axion mass for both the birefringence and the dichroism data in PVLAS. We show that the proposed value of the modulus in the RS scenario can only be accommodated for axion mass $\gsim$ 0.3 eV.