Within the Standard Model with nonlinearly realized electroweak symmetry, the LHC Higgs boson may reside in a singlet representation of the gauge group. Several new interactions are then allowed, including anomalous Higgs self-couplings, which may drive the electroweak phase transition to be strongly first-order. In this paper, we investigate the cosmological electroweak phase transition in a simplified model with an anomalous Higgs cubic self-coupling. We look at the feasibility of detecting gravitational waves produced during such a transition in the early universe by future space-based experiments. We demonstrate an intriguing interplay between collider measurements of the Higgs self-coupling and these potential gravitational wave measurements. We find that for the range of relatively large cubic couplings, [Formula: see text], [Formula: see text]mHz frequency gravitational waves can be observed by eLISA, while BBO will potentially be able to detect waves in a wider frequency range, [Formula: see text][Formula: see text]mHz.
Probing the electroweak phase transition with Higgs factories and gravitational waves
