{
  "abstract": "We investigate cosmological constraints on a $(3+1)$ neutrino framework containing an additional partially thermalized, eV-scale sterile neutrino alongside the three active species. Rather than assuming full thermalization, we allow the sterile abundance to vary independently through its physical mass $m_s$ and contribution $ΔN_{\\rm eff}$ to the effective number of relativistic species. The sterile state is modeled as a thermally distributed non-cold relic with a temperature below that of the active-neutrino background. We consider flat and non-flat $Λ$CDM and $w_0w_a$CDM cosmologies, all including the same $(3+1)ν$ sector. The models are constrained using Planck 2018 CMB data, DESI DR2 BAO, Pantheon+ Type Ia supernovae, a conservative compilation of $fσ_8$ measurements, and the recent H0DN. Oscillation-informed priors are imposed on the active-neutrino mass splittings, while the eV scale sterile-mass range is motivated by short-baseline oscillation searches and global $(3+1)$ analyses. We find that allowing additional freedom in the late-time cosmological background substantially changes the inferred sterile-neutrino sector. The effective sterile mass increases from $m_{s,\\rm eff}\\sim0.11\\pm0.05~{\\rm eV}$ in flat $Λ$CDM$+(3+1)ν$ to $\\sim0.35\\pm0.12~{\\rm eV}$ in the non-flat $w_0w_a$CDM$+(3+1)ν$ model. The corresponding sterile abundance shifts from $ΔN_{\\rm eff}\\lesssim0.1$ to $ΔN_{\\rm eff}\\simeq0.35\\pm0.15$, while remaining well below the fully thermalized limit, $ΔN_{\\rm eff}\\simeq1$. The non-flat $w_0w_a$CDM models also show $\\sim 2.8σ$ preference for open spatial geometry, $Ω_k\\simeq0.0045\\pm0.0016$, and yield $H_0\\simeq70.9\\pm0.7~{\\rm km\\,s^{-1}\\,Mpc^{-1}}$ and $S_8\\simeq0.785\\pm0.015$. These models improve the minimum $χ^2$ by approximately $21$-$25$ relative to flat $Λ$CDM$+(3+1)ν$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.10585",
  "author_total": 2,
  "authors": [
    {
      "name": "Gopal Kashyap"
    },
    {
      "name": "Kanhaiya Lal Pandey"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/e3h0899xakqcg.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.10585",
  "fulltext_url": null,
  "id": "e3h0899xakqcg",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.10585",
  "language": null,
  "licence": "CC-BY-NC-SA-4.0",
  "licence_label": "CC BY-NC-SA 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-sa/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.gen-ph"
    ],
    [
      "openalex",
      "3106|Neutrino Physics Research"
    ]
  ],
  "openalex": "W7221086423",
  "pdf_url": "https://arxiv.org/pdf/2610.10585",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/e3h0899xakqcg.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:54Z",
      "native_id": "2610.10585",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.10585"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3106|Neutrino Physics Research",
      "subfield": "high-energy"
    }
  ],
  "title": "Partially Thermalized eV-Scale Sterile Neutrinos in Dynamical Dark Energy and Non-Flat Cosmologies",
  "title_text": "Partially Thermalized eV-Scale Sterile Neutrinos in Dynamical Dark Energy and Non-Flat Cosmologies",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:54Z",
  "url": "https://research.draconitic.com/paper/e3h0899xakqcg",
  "venue": "arXiv",
  "versions": []
}