000003412 001__ 3412 000003412 005__ 20251007025150.0 000003412 0247_ $$2doi$$a10.6082/uchicago.3412 000003412 037__ $$aTHESIS$$bDissertation 000003412 041__ $$aeng 000003412 245__ $$aElectroweak Symmetry in the Early Universe 000003412 260__ $$bUniversity of Chicago 000003412 269__ $$a2021-08 000003412 300__ $$a289 000003412 336__ $$aDissertation 000003412 502__ $$bPh.D. 000003412 520__ $$aThe thermal history of the Higgs boson and its connection with electroweak symmetry breaking play an important role in the production of cosmological relics. In this thesis, I study different patterns of the electroweak symmetry at finite temperatures to build a bridge connecting particle cosmology, Higgs phenomenology and physics beyond the Standard Model, that may provide answers to some of the open questions in particle physics. I carefully scrutinize the experimental probes, e.g. measurements of the properties of the Higgs boson and gravitational wave detection, that can directly or indirectly provide information on the validity of the theories I investigate and their early universe electroweak symmetry behavior. The existence of a strong first order electroweak phase transition in the early universe is a necessary building block of the electroweak baryogenesis mechanism, that can explain the matter-antimatter asymmetry of the universe. I investigate representative extensions of the Standard Model Higgs sector, which allow for a strong first order electroweak phase transition and open opportunities for new Higgs decay channels at colliders. I study the electroweak phase transition dynamics, and the relevance of nucleation in models with an additional singlet, both in theories with SM gauge symmetries and in the case of supersymmetry. I also propose a novel scenario, where the electroweak symmetry remains broken up to very high temperatures, thereby allowing to evade strong experimental bounds from CP violation that otherwise plays important limitations on electroweak baryogenesis scenarios. Dynamics of Higgs field bubbles can directly affect the power spectrum of the gravitational wave signals generated during a strong first order phase transition. I perform a first study of the speed of the Higgs bubble wall, and show that it can be significantly slowed down by friction from particles in the hot plasma with resumed soft and collinear radiations. 000003412 540__ $$a© 2021 Yikun Wang 000003412 650__ $$aPhysics 000003412 650__ $$aParticle physics 000003412 650__ $$aTheoretical physics 000003412 653__ $$aEarly universe 000003412 653__ $$aElectroweak phase transitions 000003412 653__ $$aGravitational waves 000003412 653__ $$aHiggs physics 000003412 653__ $$aPhysics beyond the Standard Model 000003412 653__ $$aSupersymmetry 000003412 690__ $$aPhysical Sciences Division 000003412 691__ $$aPhysics 000003412 7001_ $$aWang, Yikun$$uUniversity of Chicago 000003412 72012 $$aMarcela Carena 000003412 72014 $$aMarcela Carena 000003412 72014 $$aDan Hooper 000003412 72014 $$aMark Oreglia 000003412 72014 $$aCarlos Wagner 000003412 8564_ $$95666ebf4-e5f6-46eb-ad6f-11b5b77c6283$$s7401809$$uhttps://knowledge.uchicago.edu/record/3412/files/Wang_uchicago_0330D_16026.pdf$$ePublic 000003412 909CO $$ooai:uchicago.tind.io:3412$$pDissertations$$pGLOBAL_SET 000003412 983__ $$aDissertation