{
  "abstract": "We develop a double-null framework for Cauchy-horizon dynamics in metric $f(R)$ gravity that separates ordinary mass inflation from scalaron cancellation and genuine escape from the blueshift instability. Starting from the exact spherical Hawking-mass transport equation, we show that a regular nondegenerate Cauchy horizon undergoes mass inflation whenever the effective longitudinal source is eventually nonnegative, uniformly dominates the mixed channel, and has a divergent blueshift-weighted integral. Hence bounded mass requires sufficiently strong blueshift-integrable suppression of this source or an independent competing channel. We then analyze the weaker branch in which the scalaron cancels only the leading Price-tail contribution. Under non-cancelling transverse and trace asymptotics, this forces $|R|\\to\\infty$ and an asymptotically linear high-curvature theory, $f(R)/R\\to F_->0$, where $F_-\\equiv\\lim_{v\\to\\infty}f_R$. The curvature coefficient is fixed explicitly by the transverse asymptotics. For regular model classes with a finite high-curvature $f_{RR}$ limit one obtains $f_{RR}\\to0$. More sharply, every eventually viable branch with $f_{RR}>0$ is forced to $R\\to-\\infty$ and $Λ_\\infty>-1$; the standard scalaron mass parameter then diverges, while an additional differentiable rate condition yields $m_{\\rm sc}^2\\sim F/(3f_{RR})\\to+\\infty$. In the Einstein frame the scalaron null kinetic contribution is nonnegative, so the Jordan-frame cancellation cannot be interpreted as negative scalaron null energy. The result is a local rigidity classification rather than a global theorem of strong cosmic censorship.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Phys.Rev.D 114 (2026) 8, 084082",
  "arxiv": "2609.27889",
  "author_total": 3,
  "authors": [
    {
      "name": "Francisco S. N. Lobo"
    },
    {
      "name": "Maickol Muñoz-Palma"
    },
    {
      "name": "Francisco Tello-Ortiz"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ew3b7spwb6bd9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.27889",
  "fulltext_url": null,
  "id": "ew3b7spwb6bd9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.27889",
  "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"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7214186334",
  "pdf_url": "https://arxiv.org/pdf/2609.27889",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ew3b7spwb6bd9.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:22Z",
      "native_id": "2609.27889",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.27889"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Mass inflation or scalaron rigidity: Cauchy horizons in metric f(R)",
  "title_text": "Mass inflation or scalaron rigidity: Cauchy horizons in metric f(R)",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:44Z",
  "url": "https://research.draconitic.com/paper/ew3b7spwb6bd9",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1103/nv22-96hm",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}