Sharif Digital Repository

Although the origin of matter-antimatter asymmetry remains unknown, continuing advances in theory and improved experimental limits have ruled out some scenarios for baryogenesis: for example, the sphaleron baryogenesis at the electroweak phase transition in the standard model. In this thesis, we give an introduction to some of the ideas and attempts to understand the origin of the matte -antimatter asymmetry of the universe. After the discussion of some basic issues of cosmology and particle theory, the scenarios of electroweak baryogenesis, GUT baryogenesis, and leptogenesis are outlined  

One of the open questions in particle physics and cosmology is matter-antimatter asymmetry in the Universe. Observations at different scales in the early universe indicates that the number of baryons and leptons are greater than the number of anti-baryons and anti-leptons. Various mechanisms in the last 50 years, have been proposed to generate this asymmetry from a symmetric Universe. They can be classified into two groups: models which add new particles and interactions and models which consider gravity and time dependent background fields. The basic difference is that if they respect CPT symmetry or not. In this thesis we take the second approach. We study the neutrino sector of the...