Baryon asymmetry, supersymmetry and gravitational anomalies

In this work, the authors discuss two independent issues about the baryon asymmetry of the universe. First, assuming that it is generated by an unspecified source at high temperatures, the authors study the effects of non-perturbative SU(2)w dynamics above the electroweak scale, in the context of supersymmetric models. The authors find that there is a substantial difference with the nonsupersymmetric case with the net effect of relaxing previous bounds on B and L violating interactions. In particular, supersymmetry allows neutrino masses as large as 10 eV, consistent with solar neutrino data as well as what is required for hot dark matter to explain COBE results on large scale density perturbations. It is also consistent with neutrino oscillations measureable at future accelerator experiments. Second, the authors argue that the existence of a mixed lepton number-gravitational anomaly in the standard model will induce B -- L violating interactions. These transitions would be catalyzed by Einstein-Yang-Mills instantons or sphalerons and could create a primordial B -- L asymmetry at Planck temperatures or lower. Gravity could then be the ultimate source of the baryon asymmetry. The authors analyze the viability of the presently known gravitational instantons and sphalerons to realize this scenario. 8 refs