Dilatonic current-carrying cosmic strings

2003)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 beinterpreted 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 timelikecoordinate direction; in the latter case, a phase frequency threshold occurs that is similar to whatis found in ordinary neutral current-carrying cosmic strings. We find that the dilaton contributionfor the equation of state, once averaged along the string worldsheet, vanishes, leading to an effectiveNambu-Goto behavior of such a string network in cosmology, i.e. on very large scales. It is found alsothat on small scales, the energy per unit length and tension depend on the string internal coordinatesin such a way as to permit the existence of centrifugally supported equilibrium configuration, alsoknown as vortons, whose stability, depending on the very short distance (unknown) physics, canlead to catastrophic consequences on the evolution of the Universe.