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Abstract:
Electroweak baryogenesis builds on the premise of a strong first-order electroweak
phase transition, which is realized when the temperature T at its onset and the
corresponding temperature-dependent Higgs vacuum expectation value v(T) satisfy
v(T)/T >~ 1.0 according to a standard working criterion. This thesis reassesses the
reliability of the criterion in two models with extended scalar sectors: the Inert
Doublet Model and a real scalar singlet extension of the Standard Model. The focus
lies in a reevaluation of the dominant temperature- and model-dependent effects of
the electroweak sphaleron, which underlie the criterion and determine the order of
magnitude of the condition. Furthermore, the widely neglected subtlety of successful
bubble nucleation is addressed. Its implications are comprehensively studied in the
Inert Doublet Model and generally accounted for in both models – for which recent
phenomenological constraints are taken into consideration – by evaluating the phase
transition strength at the nucleation temperature. Ultimately, the effects of the new
physics and the chosen temperature scheme on the criterion are found to be modest,
with the respective analyses of the models both suggesting an updated criterion
v(T)/ T >~ (1.05 – 1.30) that agrees well with the most generous state-of-the-art
estimates.
