Strong First-Order Electroweak Phase Transition and Gravitational Waves in a ℤ4 Fermion-Scalar Dark Matter Model
Abstract
We investigate whether a minimal ℤ4-symmetric fermion-scalar extension of the Standard Model can simultaneously realise viable dark matter, a strong electroweak phase transition, and a stochastic gravitational-wave signal. The model contains a real scalar singlet and a Dirac fermion, allowing thermal two-component dark matter, mixed WIMP-FIMP histories, and an effectively fermionic relic abundance generated by scalar decays. We impose theoretical consistency, the correct electroweak vacuum, and dark-matter constraints from relic density, direct detection, and invisible Higgs decays before using the surviving points as input for the finite-temperature analysis. This reveals that the compatibility between dark matter and a strong first-order electroweak phase transition is highly selective. After current dark-matter constraints are imposed, the strong-transition criterion along the Higgs direction is satisfied only in two viable regimes: the thermal two-component case with Mψ<MS<2Mψ and the decay-driven WIMP-FIMP case with MS>2Mψ. By contrast, the thermal regime with MS<Mψ and the stable mixed WIMP-FIMP scenario with MS<2Mψ are largely concentrated at small portal couplings or near the Higgs-resonance region, and do not yield a strong transition in the parameter space considered. The successful transitions typically proceed through an intermediate singlet-like phase. For representative nucleating benchmark points in the viable strong-transition regions, we compute the gravitational-wave spectra from sound waves and turbulence. Some spectra overlap the projected sensitivity curves of future space-based interferometers, indicating potentially observable signals in selected dark-matter-compatible regions where a sufficiently active Higgs portal appears in correlated combination with the scalar mass and the remaining dark sector parameters.
Versions
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BibTeX
@misc{carvalhocorrea2026strong,
title = {{Strong First-Order Electroweak Phase Transition and Gravitational Waves in a $\mathbbZ_4$ Fermion-Scalar Dark Matter Model}},
author = {J. P. Carvalho-Corrêa and J. P. Cunha-Melo and I. M. Pereira and B. L. Sánchez-Vega and A. C. D. Viglioni},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.11564},
eprint = {2606.11564},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.11564},
}
RIS
TY - UNPB
TI - Strong First-Order Electroweak Phase Transition and Gravitational Waves in a ℤ_4 Fermion-Scalar Dark Matter Model
AU - J. P. Carvalho-Corrêa
AU - J. P. Cunha-Melo
AU - I. M. Pereira
AU - B. L. Sánchez-Vega
AU - A. C. D. Viglioni
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2606.11564
UR - https://arxiv.org/abs/2606.11564
AB - We investigate whether a minimal ℤ_4-symmetric fermion-scalar extension of the Standard Model can simultaneously realise viable dark matter, a strong electroweak phase transition, and a stochastic gravitational-wave signal. The model contains a real scalar singlet and a Dirac fermion, allowing thermal two-component dark matter, mixed WIMP-FIMP histories, and an effectively fermionic relic abundance generated by scalar decays. We impose theoretical consistency, the correct electroweak vacuum, and dark-matter constraints from relic density, direct detection, and invisible Higgs decays before using the surviving points as input for the finite-temperature analysis. This reveals that the compatibility between dark matter and a strong first-order electroweak phase transition is highly selective. After current dark-matter constraints are imposed, the strong-transition criterion along the Higgs direction is satisfied only in two viable regimes: the thermal two-component case with M_ψ<M_S<2M_ψ and the decay-driven WIMP-FIMP case with M_S>2M_ψ. By contrast, the thermal regime with M_S<M_ψ and the stable mixed WIMP-FIMP scenario with M_S<2M_ψ are largely concentrated at small portal couplings or near the Higgs-resonance region, and do not yield a strong transition in the parameter space considered. The successful transitions typically proceed through an intermediate singlet-like phase. For representative nucleating benchmark points in the viable strong-transition regions, we compute the gravitational-wave spectra from sound waves and turbulence. Some spectra overlap the projected sensitivity curves of future space-based interferometers, indicating potentially observable signals in selected dark-matter-compatible regions where a sufficiently active Higgs portal appears in correlated combination with the scalar mass and the remaining dark sector parameters.
ER -