{
  "abstract": "Anti-ultralocality refers to the growth of spatial gradient terms relative to velocity terms in the coupled Einstein--scalar field equations. It is a characteristic feature of decelerated expansion before the onset of inflation. Previous numerical relativity studies have shown that anti-ultralocality prevents the onset of inflation in models with power-law inflaton potentials. In this paper, we show that models with plateau-shaped inflaton potentials, which are considered to be the simplest way to generate a tensor-to-scalar ratio below current observational upper limits, are especially vulnerable to anti-ultralocality effects. The reasons are the flatness of the plateau and the energy density gap of $\\sim 10$ orders of magnitude between the Planck density and the plateau potential energy. To study the problem, we develop a protocol for assessing the viability of inflationary models in general, and we apply it to a plateau potential using a previously validated numerical relativity code. We find that, starting from generic initial conditions, the growth of gradient terms in the Einstein equations relative to non-gradient terms either prevents inflation from lasting for enough $e$-folds or triggers a phase of quantum runaway. We show that the fine-tuning of initial conditions necessary to avoid these issues becomes more severe as the energy scale of inflation is made smaller, disfavoring common approaches for reducing the tensor-to-scalar ratio.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.24997",
  "author_total": 5,
  "authors": [
    {
      "name": "Joshua Shterenberg"
    },
    {
      "name": "David Garfinkle"
    },
    {
      "name": "Anna I. Rosenzweig"
    },
    {
      "name": "David Shlivko"
    },
    {
      "name": "Paul J. Steinhardt"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3z8bvj3jnr90j.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.24997",
  "fulltext_url": null,
  "id": "3z8bvj3jnr90j",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.24997",
  "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",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7204445135",
  "pdf_url": "https://arxiv.org/pdf/2608.24997",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3z8bvj3jnr90j.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:16Z",
      "native_id": "2608.24997",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.24997"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-th",
      "subfield": "high-energy"
    }
  ],
  "title": "Anti-Ultralocality and Plateau Models of Inflation",
  "title_text": "Anti-Ultralocality and Plateau Models of Inflation",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:16Z",
  "url": "https://research.draconitic.com/paper/3z8bvj3jnr90j",
  "venue": "arXiv",
  "versions": []
}