String model of the early Universe.

Abstract

Using the scaling notion of a cosmic string network, we study the evolution of the early Universe, dominated by long strings in a flat background space-time. Defining a parameter r, the radiation fraction of the total energy density, the long strings, loops, and radiation energy densities are obtained in a self-consistent manner. The reconnection of loops into long strings is obtained in a manner consistent with Kibble's one scale hypothesis. It is found that the reconnection of loops to long strings plays an important role in the evolution of the Universe. The string tension or rather G\ensuremath{\mu} is obtained and is found to vary between ${10}^{\mathrm{\ensuremath{-}}2}$ and ${10}^{\mathrm{\ensuremath{-}}4}$ as the Universe evolves from matter domination to radiation domination. It is also found that the radiation fraction is finely tuned with the string tension.