Extended Higgs Models and the Electroweak Phase Transition

Among the four fundamental forces, the electromagnetic and weak forces are unified above about 100 GeV, and are thought to have split apart via the electroweak phase transition. If this phase transition were first order, striking phenomena such as the generation of gravitational waves could occur. It is known that in the Standard Model the electroweak phase transition is not first order, but extensions with multiple Higgs bosons open the possibility of a first-order transition. This talk discusses the electroweak phase transition in such extended Higgs models.