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

Abstract

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.