Dilatonic current-carrying cosmic strings

TL;DR

This paper studies scalar-tensor gravity effects on cosmic strings, showing dilaton fields can condense inside vortices, affecting their stress-energy properties and potentially leading to stable vortons with cosmological implications.

Contribution

It introduces solutions where dilaton fields condense in cosmic strings, revealing new effects on their stress-energy tensor and stability, with implications for cosmology.

Findings

Dilaton condenses inside cosmic string cores.

Effective Nambu-Goto behavior emerges on large scales.

Existence of stable vortons with potential cosmological impact.

Abstract

We investigate the nature of ordinary cosmic vortices in some scalar-tensor extensions of gravity. We find solutions for which the dilaton field condenses inside the vortex core. These solutions can be interpreted as raising the degeneracy between the eigenvalues of the effective stress-energy tensor, namely the energy per unit length U and the tension T, by picking a privileged spacelike or timelike coordinate direction; in the latter case, a phase frequency threshold occurs that is similar to what is found in ordinary neutral current-carrying cosmic strings. We find that the dilaton contribution for the equation of state, once averaged along the string worldsheet, vanishes, leading to an effective Nambu-Goto behavior of such a string network in cosmology, i.e. on very large scales. It is found also that on small scales, the energy per unit length and tension depend on the string internal coordinates in such a way as to permit the existence of centrifugally supported equilibrium configuration, also known as vortons, whose stability, depending on the very short distance (unknown) physics, can lead to catastrophic consequences on the evolution of the Universe.