{
  "abstract": "A photon coupled non-minimally to the Weyl tensor propagates differently in its two linear polarization states: the vacuum around a black hole becomes a birefringent medium. On a Schwarzschild background the coupling $α$ splits the photon sphere and the critical impact parameter of the two polarizations, producing a double shadow and a polarization-dependent photon ring; the two shadow edges separate by $62\\%$ of the shadow radius at $α/M^2=0.75$. We compute a unified set of wave-optical and geometric-optical observables for both polarizations across a range of $α$: greybody factors, absorption cross sections, differential cross sections and their glories, a backward birefringence signal, shadows, photon rings, and null trajectories. The two-polarization scattering matrices are extracted with a Riccati--Hankel matching scheme that keeps the phase-sensitive observables reliable, and the geometric-optics chain is cross-validated with three independent ray tracers. The cleanest diagnostic is the backward signal: it is protected by parity and vanishes identically at $α=0$.Laboratory bounds on $α$ render these effects unobservable for supermassive black holes; order-unity couplings would require a black hole of primordial mass.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: JCAP 10 (2026) 036",
  "arxiv": "2607.10658",
  "author_total": 2,
  "authors": [
    {
      "name": "Mao-Yuan Wan"
    },
    {
      "name": "Chen Wu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/0mhqkfymn6sdh.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.10658",
  "fulltext_url": null,
  "id": "0mhqkfymn6sdh",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.10658",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "gr-qc"
    ],
    [
      "arxiv",
      "hep-th"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2607.10658",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-13",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/0mhqkfymn6sdh.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:29:50Z",
      "native_id": "2607.10658",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.10658"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-th",
      "subfield": "high-energy"
    }
  ],
  "title": "Polarization-dependent observational signatures of Weyl-coupled photons around a black hole",
  "title_text": "Polarization-dependent observational signatures of Weyl-coupled photons around a black hole",
  "type": "preprint",
  "updated_at": "2026-10-30T12:29:50Z",
  "url": "https://research.draconitic.com/paper/0mhqkfymn6sdh",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1088/1475-7516/2026/10/036",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}