Wall of fundamental constants

Abstract

We consider the signatures of a domain wall produced in the spontaneous symmetry breaking involving a dilatonlike scalar field coupled to electromagnetism. Domains on either side of the wall exhibit slight differences in their respective values of the fine-structure constant, $\ensuremath{\alpha}$. If such a wall is present within our Hubble volume, absorption spectra at large redshifts may or may not provide a variation in $\ensuremath{\alpha}$ 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 $\ensuremath{\alpha}$ based on Keck/Hires data and of the constancy of $\ensuremath{\alpha}$ based on Very Large Telescope data. We derive the properties of the wall and the parameters of the underlying microscopic model required to reproduce the possible spatial variation of $\ensuremath{\alpha}$. 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.