Two-Component Dark Matter and Strongly First-Order Electroweak Phase Transition via a Two-Step Mechanism in the Inert Doublet plus Real Singlet Model
Abstract
We study a two-component dark matter model in which a real singlet scalar and an inert doublet scalar are simultaneously present alongside the Standard Model, each stabilized by an independent discrete symmetry. The real singlet undergoes a strong first-order transition at high temperature, establishing an intermediate phase with a non-zero singlet vacuum expectation value, which in turn generates the barrier required for the Higgs field to complete a strongly first-order electroweak transition at a lower temperature. This two-step mechanism naturally enforces the condition vc/Tc ≥ 1, the sphaleron washout-avoidance criterion necessary for electroweak baryogenesis. The gravitational wave spectrum from both steps is computed; the second step produces a decihertz signal, peaking near $0.08−−0.34~\mathrm{Hz}$ across the viable parameter space and $0.14−−0.22~\mathrm{Hz}$ at the benchmark points, that reaches the sensitivity of DECIGO for the strongest transitions and of BBO more widely, while the first remains sub-threshold for all planned detectors. At the coupling values required to drive the phase transition, the singlet is generically underabundant as a thermal relic, so the inert doublet carries the dominant fraction of the observed relic density. Confronting the model with current constraints, we find that the LUX-ZEPLIN 2024 result excludes the entire electroweak-phase-transition-viable parameter space of the singlet sector across the full mass range, even after rescaling by the singlet relic fraction, establishing a complete no-go for the singlet as a viable thermal dark matter candidate in this framework.
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BibTeX
@misc{naik2026twocomponent,
title = {{Two-Component Dark Matter and Strongly First-Order Electroweak Phase Transition via a Two-Step Mechanism in the Inert Doublet plus Real Singlet Model}},
author = {Deeksha Dattaram Naik and Arnab Chaudhuri},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28014},
eprint = {2610.28014},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28014},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Two-Component Dark Matter and Strongly First-Order Electroweak Phase Transition via a Two-Step Mechanism in the Inert Doublet plus Real Singlet Model
AU - Deeksha Dattaram Naik
AU - Arnab Chaudhuri
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28014
UR - https://arxiv.org/abs/2610.28014
AB - We study a two-component dark matter model in which a real singlet scalar and an inert doublet scalar are simultaneously present alongside the Standard Model, each stabilized by an independent discrete symmetry. The real singlet undergoes a strong first-order transition at high temperature, establishing an intermediate phase with a non-zero singlet vacuum expectation value, which in turn generates the barrier required for the Higgs field to complete a strongly first-order electroweak transition at a lower temperature. This two-step mechanism naturally enforces the condition v_c/T_c ≥ 1, the sphaleron washout-avoidance criterion necessary for electroweak baryogenesis. The gravitational wave spectrum from both steps is computed; the second step produces a decihertz signal, peaking near $0.08−−0.34~\mathrm{Hz}$ across the viable parameter space and $0.14−−0.22~\mathrm{Hz}$ at the benchmark points, that reaches the sensitivity of DECIGO for the strongest transitions and of BBO more widely, while the first remains sub-threshold for all planned detectors. At the coupling values required to drive the phase transition, the singlet is generically underabundant as a thermal relic, so the inert doublet carries the dominant fraction of the observed relic density. Confronting the model with current constraints, we find that the LUX-ZEPLIN 2024 result excludes the entire electroweak-phase-transition-viable parameter space of the singlet sector across the full mass range, even after rescaling by the singlet relic fraction, establishing a complete no-go for the singlet as a viable thermal dark matter candidate in this framework.
ER -