Higgs Self-Coupling as a Probe of Electroweak Phase Transition

We argue that, within a broad class of extensions of the Standard Model, there is a tight corellation between the dynamics of the electroweak phase transition and the cubic self-coupling of the Higgs boson: Models which exhibit a strong first-order EWPT predict a large deviation of the Higgs self-coupling from the Standard Model prediction, as long as no accidental cancellations occur. Order-one deviations are typical. This shift would be observable at the Large Hadron Collider if the proposed luminosity or energy upgrades are realized, as well as at a future electron-positron collider such as the proposed International Linear Collider. These measurements would provide a laboratory test of the dynamics of the electroweak phase transition.