{
  "abstract": "We show that black-hole rotation and an external magnetic field can jointly generate a distinct class of scalar clouds. Using the Kerr-Bertotti-Robinson geometry as a separable laboratory for magnetized rotating black holes, we study a charged massive scalar field and map the radial Klein-Gordon equation into a one-dimensional Schrödinger-like form. The magnetic coupling shifts the near-horizon dispersion relation and realizes a positive horizon gap: a sufficient near-horizon criterion under which the horizon wavenumber becomes purely imaginary in a finite frequency band below the usual kinematic synchronization frequency. In this band the physical horizon boundary condition is no longer a propagating ingoing wave, but a regular exponentially decaying state. This rotation-magnetic-field mechanism quenches the superradiant flux and supports horizon-decaying scalar clouds (Type-II), distinct from the usual synchronized propagating clouds (Type-I). Matched asymptotic expansions and numerical shooting solutions are used to exhibit both branches and their spatial profiles. Thus the Kerr-Bertotti-Robinson solution is not an isolated curiosity, but an explicit realization of a broader positive-gap criterion for horizon-evanescent stationary configurations that are absent in isolated Kerr systems.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: JHEP 09 (2026) 283",
  "arxiv": "2606.27958",
  "author_total": 3,
  "authors": [
    {
      "name": "Hengyu Xu"
    },
    {
      "name": "Haowei Chen"
    },
    {
      "name": "Shao-Jun Zhang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/atvcxp1ayks61.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.27958",
  "fulltext_url": null,
  "id": "atvcxp1ayks61",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.27958",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "gr-qc"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2606.27958",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/atvcxp1ayks61.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:31Z",
      "native_id": "2606.27958",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.27958"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Horizon-Evanescent Scalar Clouds from Coupled Rotation and Magnetic Fields around Black Holes",
  "title_text": "Horizon-Evanescent Scalar Clouds from Coupled Rotation and Magnetic Fields around Black Holes",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:31Z",
  "url": "https://research.draconitic.com/paper/atvcxp1ayks61",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1007/jhep09(2026)283",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}