{
  "abstract": "The global topology of the Universe is a longstanding open question. In this work, we examine the statistical signatures of a positively curved universe with a Friedmann--Lemaitre--Robertson--Walker metric and the topology of a lens space $L(p,q)$. Since these manifolds are generally statistically anisotropic and inhomogeneous, their cosmic microwave background (CMB) covariance matrices contain non-zero off-diagonal entries that depend on observer location. We compute these full harmonic-space covariance matrices for scalar perturbations for arbitrary lens spaces and observer position. Using the Kullback--Leibler divergence, we assess the distinguishability of these spaces from a simply connected three-sphere with the same curvature. The results show that topological signatures can still be significant in a cosmic-variance-limited regime even when the length, $d_{\\rm NC}$, of the shortest loop around the Universe through the observer exceeds the diameter, $d_{\\rm LSS}$, of the last-scattering surface by up to $10\\%$. This distinguishability depends on the curvature, the lens space and the observer position mainly through the ratio $d_{\\rm NC}/d_{\\rm LSS}$, which is set not only by the curvature radius but also by $p$, $q$ and the observer location. Therefore, for any value of the spatial curvature, however small, there are lens spaces and observer positions for which $0.985\\,d_{\\rm LSS}<d_{\\rm NC}<1.1\\,d_{\\rm LSS}$. Such observers would find no matched circles in the CMB large enough to have been detected to date, yet the topology would remain potentially discoverable through its statistical signatures.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.12418",
  "author_total": 19,
  "authors": [
    {
      "name": "Mikel Martin Barandiaran"
    },
    {
      "name": "Catherine Petretti"
    },
    {
      "name": "Stefano Anselmi"
    },
    {
      "name": "Deyan P Mihaylov"
    },
    {
      "name": "Anna Negro"
    },
    {
      "name": "Glenn D Starkman"
    },
    {
      "name": "Andrius Tamosiunas"
    },
    {
      "name": "Yashar Akrami"
    },
    {
      "name": "George Alestas"
    },
    {
      "name": "Javier Carrón Duque"
    },
    {
      "name": "Craig J Copi"
    },
    {
      "name": "Fernando Cornet-Gomez"
    },
    {
      "name": "Linn Htat Lu"
    },
    {
      "name": "Andrew H Jaffe"
    },
    {
      "name": "Arthur Kosowsky"
    },
    {
      "name": "José Javier Ortega Gómez"
    },
    {
      "name": "Ricardo G Rodrigues"
    },
    {
      "name": "Amirhossein Samandar"
    },
    {
      "name": "Cynthia Trendafilova"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ccbt57wq8p8jr.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.12418",
  "fulltext_url": null,
  "id": "ccbt57wq8p8jr",
  "issns": [],
  "landing_url": "https://hal.science/hal-05842226v1",
  "language": "en",
  "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",
      "astro-ph.CO"
    ],
    [
      "hal",
      "0.phys"
    ],
    [
      "hal",
      "1.phys.astr"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7221159679",
  "pdf_url": "https://arxiv.org/pdf/2610.12418",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-08",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ccbt57wq8p8jr.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:02Z",
      "native_id": "hal-05842226",
      "source": "hal",
      "url": "https://hal.science/hal-05842226v1"
    },
    {
      "first_seen": "2026-10-30T12:27:54Z",
      "native_id": "2610.12418",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.12418"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "physics",
      "origin": "hal:0.phys",
      "subfield": "general"
    }
  ],
  "title": "Cosmic topology. Part IId. Eigenmodes and correlation matrices of lens spaces",
  "title_text": "Cosmic topology. Part IId. Eigenmodes and correlation matrices of lens spaces",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:54Z",
  "url": "https://research.draconitic.com/paper/ccbt57wq8p8jr",
  "venue": "HAL",
  "versions": []
}