arXiv subjects

Alexei H. Sopov

Publications and source records attributed to Alexei H. Sopov.

3 recordsLinked to original sources

arXiv2026

Dark Matter Freeze-in from a $Z^\prime$ Reheaton

We consider the Standard Model (SM) extended by a secluded $U(1)_D$ gauge sector encompassing a Dirac fermion ($χ$) dark matter (DM), an abelian gauge boson $Z^\prime$ and a SM-singlet complex-scalar field $Φ$, whose radial component drives cosmic inflation. When the Higgs portal coupling is small, the $Z^\prime$ then acts as a {\it ``reheaton''}, dominating the energy budget of the Universe before finally yielding the SM bath, with reheating temperature $< O(10)$ TeV, through the gauge portal interaction. We explore the possibility that DM freezes-in via non-thermal $Z^\prime$ decays before reheating ends, giving rise to substantial viable parameter space. We account for non-perturbative effects, relevant during the initial stages of reheating, using lattice simulations. We additionally show how the cosmological gravitational wave (GW) background produced by preheating and inflation allow for a direct probe of the reheating mechanism.

hep-ph↗

arXiv2025

The post-inflationary cosmology of the VISH$ν$ axion-majoron model

It was previously shown how several explanatory deficiencies of the Standard Model (including the origin of dark matter, matter-antimatter asymmetry, small active neutrino mass, strong CP-conservation and the seeds for large-scale structure formation) may be economically resolved when an experimentally-accessible QCD axion also plays the role of the majoron, and the scalar partner of the axion is dynamical during inflation. In this paper, we complete this general study of the cosmological history for a unit domain-wall number option of the DFSZ-type, dubbed VISH$ν$, by performing a detailed lattice-informed analysis of the reheating era. In doing so, we make inflationary and leptogenesis predictions more precise through estimates of the reheating temperature and the expansion history. The viable reheating scenarios, which at the same time satisfy strict conditions for naturalness (radiative stability), are also shown to respect dark radiation bounds. We also characterise the high-frequency spectrum of gravitational waves, and mention other phenomenological implications that distinguish VISH$ν$ from alternative proposals.

hep-ph↗

arXiv2022

VISH$ν$: a unified solution to five SM shortcomings with a protected electroweak scale

We propose a Standard Model extension, coined VISH$ν$ (Variant-axIon Seesaw Higgs $ν$-trino), that is an $N_{\text{DW}} = 1$ variation of its predecessor, the $ν$DFSZ model. In accounting for the origin of neutrino masses, dark matter and the baryon asymmetry of the universe, VISH$ν$ inherits the explanatory power of $ν$DFSZ while, of course, resolving the strong $CP$ problem. In both models, the electroweak scale is naturally protected from a high seesaw scale that is identified with the Peccei-Quinn (PQ) spontaneous symmetry breaking scale. Through a flavour variant coupling structure, VISH$ν$ evades a domain wall problem, extending the cosmological reach of the $ν$DFSZ to include a viable period of inflation. The primary focus of this paper is on the inflationary dynamics of VISH$ν$ and their naturalness in the sense of radiative stability. We find that non-minimal gravitational couplings, generically developed by the VISH$ν$ scalar fields, naturally support a viable inflaton field which typically has both a PQ scalar and Higgs component. An axion mass window [$40μ\text{eV}, \sim 2\text{meV}$] accessible to forthcoming searches, results for the case where PQ symmetry is restored during the (p)reheating phase.

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