Hieu The Pham | Searcharxiv

arXiv2026

Gravitational waves from CP domain wall collapse and electron EDM in a complex singlet model with dimension-five Yukawa interactions

We study the interplay between gravitational waves (GWs) from domain wall collapse and the electron electric dipole moment (EDM) in a complex singlet extension of the standard model with dimension-five Yukawa interactions. In this framework, the scalar potential admits CP-related degenerate vacua, leading to the formation of CP domain walls. While the resulting GW signal provides a probe of the vacuum structure of the singlet scalar sector, it does not by itself constitute a CP-violating observable. Once the singlet scalar is coupled to standard model fermions, CP-violating phases become observable through EDMs. We analyze whether current and future EDM experiments can probe the parameter region where the GW signal is detectable by SKA and THEIA. We find that the current electron EDM bound already constrains part of the parameter space, while future sensitivities at the level of $10^{-31}$--$10^{-32}\,e\,\mathrm{cm}$ can probe regions overlapping with the GW-detectable domain. Our results highlight the complementarity between GW and EDM observables in probing the singlet scalar sector, providing a coherent picture of its vacuum structure and CP properties.

hep-ph↗

arXiv2024

Gravitational waves from domain wall collapses and dark matter in the SM with a complex scalar

We study domain wall induced by spontaneously broken $\mathbb{Z}_2$ symmetry and its gravitational wave signature in the standard model with a complex scalar in connection with dark matter physics. In a minimal setup, a linear term of the singlet field is added to the scalar potential as an explicit $\mathbb{Z}_2$ breaking term to make the domain wall unstable. We obtain its minimal size from cosmological constraints and show that the parameter space that can be probed by current and future pulsar time array experiments requires the vacuum expectation value of the singlet field to be greater than $\mathcal{O}(10-100)$ TeV, along with a singlet-like Higgs mass of $\mathcal{O}(1-100)$ TeV. However, such a region is severely restricted by the dark matter relic density, which places an upper bound on the singlet vacuum expectation value at approximately 200 TeV, and limits the dark matter mass to about half of the singlet-like Higgs boson mass.

hep-ph↗