{
  "abstract": "In this paper, we formulate a ghost-free metric-affine scalar-torsion model in which a pseudoscalar field is coupled to the Nieh--Yan density and derivatively coupled to the Einstein-Palatini tensor. The theory is projectively invariant and, in the shift-symmetric sector, depends on the scalar field only through its gradient. After fixing the projective gauge, the independent connection is solved exactly: its symmetric part is the Levi-Civita connection associated with the metric $h_{μν}$, disformally related to the metric $g_{μν}$, while its antisymmetric part is a purely axial torsion sourced by $v_μ=\\partial_μ\\vartheta$. We identify a degenerate ghost-free branch, $α=6β^2κ^2$, for which Ricci-flat geometries in the $h$-metric frame solve the metric equations and the Noether current vanishes identically. For example, we consider Schwarzschild and Kerr geometries in the $h$-metric frame, which generate disformal deformations on these geometries from the perspective of the $g$-metric frame. For the Schwarzschild black hole in the $h$-metric frame, we construct static and Babichev--Charmousis-like time-dependent scalar profiles, and discuss horizon regularity in Eddington--Finkelstein coordinates. For the Kerr black hole in the $h$-metric frame, we show that regularity on the rotation axis rules out a nontrivial globally real static fixed-norm scalar profile. For the stationary time-dependent branch, axis regularity and asymptotic reality fix $Y_0=-q^2$ and eliminate the angular dependence, yielding a nontrivial future-regular profile in ingoing Kerr coordinates. The Kerr solution with the nontrivial scalar field is stealth only in the $h$-metric frame. In the $g$-metric frame, it produces disformal corrections stemming from the nontrivial scalar field profile and it represents secondary disformal scalar hair rather than primary Noether-charge hair.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2606.24041",
  "author_total": 5,
  "authors": [
    {
      "name": "E. Brito"
    },
    {
      "name": "G. Macedo"
    },
    {
      "name": "J. R. Nascimento"
    },
    {
      "name": "A. Yu. Petrov"
    },
    {
      "name": "P. J. Porfírio"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/50v4f7wyafz5c.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.24041",
  "fulltext_url": null,
  "id": "50v4f7wyafz5c",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.24041",
  "language": null,
  "licence": "CC0-1.0",
  "licence_label": "CC0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/publicdomain/zero/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "gr-qc"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7165802685",
  "pdf_url": "https://arxiv.org/pdf/2606.24041",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/50v4f7wyafz5c.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:22Z",
      "native_id": "2606.24041",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.24041"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Nonrotating and rotating black holes with secondary disformal hair in a ghost-free metric-affine parity-violating scalar-torsion theory",
  "title_text": "Nonrotating and rotating black holes with secondary disformal hair in a ghost-free metric-affine parity-violating scalar-torsion theory",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:44Z",
  "url": "https://research.draconitic.com/paper/50v4f7wyafz5c",
  "venue": "arXiv",
  "versions": []
}