Study of electroweak phase transition and relevance to electroweak baryogenesis.

The Universe is known to be asymmetric in the number of baryons to antibaryons in the ratio of 109 parts to 1. Though the Grand Unified Theories (GUTs) were able to generate this asymmetry dynamically yet, they faced a number of problems in the form of nonobservation of proton decay and production of monopoles. An alternative model was searched for in the electroweak theory, which has all the characteristics required for a viable baryogenesis mechanism leading to the baryon asymmetry of the Universe: (i) the electroweak anomaly can induce significant baryon number violation at high temperatures; (ii) the CP violation comes from the Kobayashi Maskawa phase and (iii) the electroweak phase transition is considered to be of first order. But investigations show that, the minimal standard model with one Higgs doublet can not provide the right amount of CP violation needed to explain the baryon asymmetry of the Universe. The generated asymmetrY can also get wiped out by sphalaeronic transition, if the Higgs is heavier than 50 GeV. More Info

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