Gravitational waves from the phase transition of a nonlinearly realized electroweak gauge symmetry

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, 111 GeV less than or similar to vertical bar kappa vertical bar less than or similar to 118 GeV, similar to mHz frequency gravitational waves can be observed by eLISA, while BBO will potentially be able to detect waves in a wider frequency range, 0.1-10 mHz.