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Fermion-Induced Electroweak Symmetry Non-Restoration via Temperature-Dependent Masses

Thesis Defense

12:00 pm–2:00 pm
Jorgensen Hall Room: 207
Physics Department, (402) 472-2770,
Yu Hang Ng will defend his thesis, “Fermion-Induced Electroweak Symmetry Non-Restoration via Temperature-Dependent Masses” via Zoom and in-person.

Abstract: Standard Model (SM) and many extensions of SM predict that the electroweak (EW) symmetry was restored in the early universe when the temperature was around 160 GeV. However, recent studies showed that the interactions between some new scalars and SU(2)_L Higgs doublet(s) can cause the EW symmetry to remain broken at temperatures well above the EW scale in certain renormalizable extensions of SM. In this study, we found that new fermions from renormalizable models can also induce this EW symmetry non-restoration effect, provided that they have the appropriate temperature-dependent masses. These masses can arise naturally from the interactions between the new fermions and scalar fields. I will present these models, the higher-order corrections, and the theoretical and experimental constraints that must be taken into account. Then, I will discuss the novel thermal histories predicted by these models within the allowed parameter space. Certain cases predict that the EW phase transitions are strongly first-order and occur at temperatures much higher than the EW scale. I will discuss the prospect of detecting the stochastic gravitational-wave background from these cosmological phase transitions at future gravitational wave observatories, such as BBO and DECIGO.

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This event originated in Physics.