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Multi-step Strong First-Order Electroweak Phase Transitions in the Inverted Type-I 2HDM: Parameter Space, Gravitational Waves, and Collider Phenomenology
Soojin Lee, Dongjoo Kim, Jin-Hwan Cho, Jinheung Kim, Jeonghyeon Song
https://arxiv.org/abs/2506.03260

Multi-step Strong First-Order Electroweak Phase Transitions in the Inverted Type-I 2HDM: Parameter Space, Gravitational Waves, and Collider Phenomenology
We investigate the nature of the electroweak phase transition (EWPT) in the Type-I two-Higgs-doublet model under the inverted Higgs scenario, where the observed 125 GeV Higgs boson corresponds to the heavier \textit{CP}-even scalar. We systematically map the parameter space viable for strong first-order EWPTs (SFOEWPTs) under current theoretical and experimental constraints, revealing that such transitions can occur through one-step, two-step, and rarely three-step pathways with distinct phenom…