String-Mediated Electroweak Baryogenesis: A Critical Analysis

We study the scenario of electroweak baryogenesis mediated by nonsuperconducting cosmic strings. This idea relies upon electroweak symmetry being restored in a region around the core of the topological defect so that, within this region, the rate of baryon number violation is enhanced. We compute numerically how effectively baryon number is violated along a cosmic string, at an epoch when the baryon number violation rate elsewhere is negligible. We show that B-violation along nonsuperconducting strings is quite inefficient. When proper accounting is taken of the velocity dependence of the baryon number production by strings, it proves too small to explain the observed abundance by at least ten orders of magnitude, whether the strings are in the friction dominated or the scaling regime. CERN-TH/98-306 October 1998 CERN-TH/98-306 IEM-FT-182/98 MCGILL-98/24 hep-ph/9810261 e-mail: [email protected] e-mail: [email protected] e-mail: [email protected] e-mail: [email protected]. On leave of absence from Theoretical Physics Department, University of Oxford, UK.