Candidate: Supervisor:

A possible connection between the dark matter and strong first order elec-troweak phase transition, which is an essential ingredient of the electroweak baryogenesis, has been explored in this thesis. It is shown that the extension of the Standard Model’s minimal Higgs sector with an inert SU(2)L scalar doublet can provide light dark matter candidate and simultaneously induce a strong first order phase transition. There is however no symmetry reason to prevent the extension using scalars with higher SU(2)L representations. Therefore, by making random scans over the models ’ parameters, we show, in the light of electroweak physics constraints, strong first order electroweak phase transition and the possibility of having a sub-TeV cold dark matter candidate, that the higher representations are rather disfavored compared to the inert doublet. This is done by computing generic perturbativity be-havior and impact on electroweak phase transitions of higher representations in comparison with the inert doublet model. Explicit phase transition an