Fate of electroweak symmetry in the early Universe: Non-restoration and trapped vacua in the N2HDM
G. Weiglein, Heinemeyer, Sven, No, Jose Miguel, José Miguel No, S. Heinemeyer
Abstract
Extensions of the Standard Model (SM) Higgs sectorallow for a rich cosmological history around the electroweak(EW) scale. We show that besides strong firstorder phase transitions, which have thoroughly been studied in the literature in two-Higgs doublet models (2HDM),in the context of the next-to 2HDM (N2HDM)other phenomena like EW symmetry non-restoration or vacuum trappingcan occur in certain regions of theparameter space.Focusing on the type~II N2HDM and taking into accountvarious theoretical and experimental constraints,we demonstrate how these novel finite-temperatureeffects are related and how they can be used to furtherconstrain the parameter space of the model.In particular, we show that the presenceof global EW minimum at zero temperature mightnot be a sufficient requirement for the validityof the vacuum configuration. Moreover, weargue that a calculation of the tunneling probabilityis required to accurately predict the thermalhistory of a parameter point, whereas the appearanceof a critical temperature at which the EW phase becomes the deepest minimum is not sufficientfor a transition to take place.