{
  "abstract": "Near thermal equilibrium, the transverse momentum density in a fluid diffuses according to $ω(k) \\sim - i {\\cal D} k^2$ at small $k$, where the diffusion coefficient ${\\cal D}$ is proportional to the shear viscosity. In field theories with a holographic dual description in terms of classical gravity, the shear-mode frequency $ω(k)$ approaches the light cone at large imaginary wave vector. We develop a WKB approach to study this limit. For black branes in AdS$_{p+2}$, we determine the leading terms of the asymptotic large-$k$ expansion of the shear-mode frequency $ω(k)$. In the case of AdS$_{5}$, we compute a large number of terms of this series and use resummation techniques to analytically continue the result to small $k$. We find strong evidence that $ω(k)$ is analytic at $k=0$ and vanishes there, which amounts to the existence of hydrodynamics encoded in the large-$k$ physics. Taking 10 terms in the large-$k$ expansion of $ω(k)$ gives an answer for ${\\cal D}$ which is accurate to better than $0.5\\%$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.32892",
  "author_total": 4,
  "authors": [
    {
      "name": "Inês Aniceto"
    },
    {
      "name": "Pavel Kovtun"
    },
    {
      "name": "Alex Ratcliffe"
    },
    {
      "name": "Michał Spaliński"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3bkjk03nzy7ke.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.32892",
  "fulltext_url": null,
  "id": "3bkjk03nzy7ke",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.32892",
  "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",
      "hep-th"
    ],
    [
      "openalex",
      "3106|Black Holes and Theoretical Physics"
    ]
  ],
  "openalex": "W7223663773",
  "pdf_url": "https://arxiv.org/pdf/2610.32892",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-23",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3bkjk03nzy7ke.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:15Z",
      "native_id": "2610.32892",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.32892"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-th",
      "subfield": "high-energy"
    }
  ],
  "title": "Shear viscosity from complex light-cone expansion",
  "title_text": "Shear viscosity from complex light-cone expansion",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:15Z",
  "url": "https://research.draconitic.com/paper/3bkjk03nzy7ke",
  "venue": "arXiv",
  "versions": []
}