The Wall of Fundamental Constants

TL;DR

This paper explores a domain wall model involving a scalar field that causes spatial variations in the fine-structure constant alpha, potentially explaining conflicting observational claims about alpha's constancy.

Contribution

It introduces a novel domain wall scenario involving a dilaton-like scalar field that could account for observed variations in alpha and reconcile conflicting data.

Findings

Domain walls can produce measurable spatial variations in alpha.

The model parameters can be tuned to match observational data.

Constraints on the existence of such walls are derived from observational limits.

Abstract

We consider the signatures of a domain wall produced in the spontaneous symmetry breaking involving a dilaton-like scalar field coupled to electromagnetism. Domains on either side of the wall exhibit slight differences in their respective values of the fine-structure constant, alpha. If such a wall is present within our Hubble volume, absorption spectra at large redshifts may or may not provide a variation in alpha relative to the terrestrial value, depending on our relative position with respect to the wall. This wall could resolve the ``contradiction'' between claims of a variation of alpha based on Keck/Hires data and of the constancy of alpha based on VLT data. We derive the properties of the wall and the parameters of the underlying microscopic model required to reproduce the possible spatial variation of alpha. We discuss the constraints on the existence of the low-energy domain wall and describe its observational implications concerning the variation of the fundamental constants.