{
  "abstract": "We study a massive scalar field on the rotating Kalb–Ramond black hole of Kumar et al. [7], near extremality in $$(a,\\gamma ,\\lambda )$$ ( a , γ , λ ) . The Klein–Gordon–Fock equation separates, with $$\\Lambda _\\textrm{rad}=\\Lambda _\\textrm{ang}+a^{2}\\omega ^{2}-2am\\omega $$ Λ rad = Λ ang + a 2 ω 2 - 2 a m ω . At extremality $$\\Delta $$ Δ and K ( r ) share a zero, keeping $$K^{2}/\\Delta $$ K 2 / Δ regular and reducing the radial problem to Whittaker form on the Kerr line $$\\gamma =0$$ γ = 0 and the Kerr–Newman line $$\\lambda =1$$ λ = 1 . Stationary resonances saturate $$\\omega =m\\,\\Omega _{H}$$ ω = m Ω H with $$\\mu _\\textrm{cloud}>m\\,\\Omega _{H}$$ μ cloud > m Ω H , overtones accumulating from above. In the genuine Kalb–Ramond interior $$0<\\lambda <1$$ 0 < λ < 1 no such reduction exists; we solve the exact radial equation numerically, validated against the closed forms to eleven digits. Off extremality, $$a=a_\\textrm{ext}(1-\\delta ^{2})$$ a = a ext ( 1 - δ 2 ) , the clouds join the co-rotating zero-damped branch $$\\omega _{n}=m\\,\\Omega _{H}-i\\,\\kappa \\,(n+\\tfrac{1}{2}+\\beta )$$ ω n = m Ω H - i κ ( n + 1 2 + β ) , governed by the near-horizon exponent $$\\beta $$ β and distinct from the photon-sphere family. Greybody factors and superradiance follow from direct integration, recovering the classical $$\\ell =m=1$$ ℓ = m = 1 Kerr result. Strong-field lensing follows in the Bozza–Tsukamoto limit, the shadow from Carter separation. Intersecting the Event Horizon Telescope window of Zubair et al. [8] with our cloud-existence region bounds $$(\\gamma ,\\lambda )$$ ( γ , λ ) more tightly than either alone.",
  "abstract_shown": true,
  "affiliations": [
    "Cyprus International University",
    "Eastern Mediterranean University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Gülnihal Aydemir",
      "orcid": "0000-0001-7270-4355"
    },
    {
      "affs": [
        1
      ],
      "name": "İzzet Sakallı",
      "orcid": "0000-0001-7827-9476"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/4tkmc8g6t3053.bib",
  "cited_by": 0,
  "doi": "10.1140/epjc/s10052-026-16352-1",
  "fulltext_url": "https://doi.org/10.1140/epjc/s10052-026-16352-1",
  "id": "4tkmc8g6t3053",
  "issns": [
    "1434-6044",
    "1434-6052"
  ],
  "landing_url": "https://link.springer.com/article/10.1140/epjc/s10052-026-16352-1",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0",
  "metadata_licence": null,
  "native_subjects": [
    [
      "lcc",
      "QB460-466"
    ],
    [
      "lcc",
      "QC770-798"
    ],
    [
      "openalex",
      "3106|Black Holes and Theoretical Physics"
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  "openalex": "W7223403590",
  "pdf_url": "https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16352-1.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-23",
  "publisher": "Springer Science and Business Media LLC",
  "ris": "https://research.draconitic.com/paper/4tkmc8g6t3053.ris",
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    {
      "first_seen": "2026-10-30T12:18:04Z",
      "native_id": "10.1140/epjc/s10052-026-16352-1",
      "source": "crossref",
      "url": "https://link.springer.com/article/10.1140/epjc/s10052-026-16352-1"
    },
    {
      "first_seen": "2026-10-30T13:46:27Z",
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      "url": "https://doi.org/10.1140/epjc/s10052-026-16352-1"
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  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3106|Black Holes and Theoretical Physics",
      "subfield": "high-energy"
    }
  ],
  "title": "Stationary scalar clouds, quasinormal ringing, and observational signatures of (near-)extremal rotating Kalb–Ramond black holes: from the superradiant threshold to EHT bounds",
  "title_text": "Stationary scalar clouds, quasinormal ringing, and observational signatures of (near-)extremal rotating Kalb–Ramond black holes: from the superradiant threshold to EHT bounds",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T13:46:27Z",
  "url": "https://research.draconitic.com/paper/4tkmc8g6t3053",
  "venue": "The European Physical Journal C",
  "versions": []
}