Phase Transitions in the Two-Higgs-Doublet Model with a Softly-Broken Z2 Symmetry

Sammanfattning: The two-Higgs-doublet model (2HDM) is an extension to the Standard Model which adds a second Higgs doublet. This extension provides freedom within the model, in comparison to the Standard Model, which makes it possible to study strong electroweak phase transitions. These can provide an explanation for the matter-antimatter asymmetry through the Sakharov conditions, three conditions that leads to creating this asymmetry in the early universe. Due to this, we are looking at phase transitions in the 2HDM extension to the Standard Model. This is done by using an effective field theory, dimensional reduction, that allows to study thermal effects in the model. Using this, a search is done which finds strong phase transitions for certain parameters. These results are compared to another method that has been previously used without finding a good similarity between the results for the different methods.