Cosmic strings in Bekenstein-type models

Abstract

We study static cosmic string solutions in the context of Bekenstein-type models. We show that there is a class of models of this type for which the classical Nielsen-Olesen vortex is still a valid solution. However, in general static string solutions in Bekenstein-type models strongly depart from the standard Nielsen-Olesen solution with the electromagnetic energy concentrated along the string core seeding spatial variations of the fine structure constant, $α$. We consider models with a generic gauge kinetic function and show that equivalence principle constraints impose tight limits on the allowed variations of $α$ induced by string networks on cosmological scales.

13 pages, 5 figures, error in ref. [38] corrected, references added, discussion extended