{
  "abstract": "The global spatial structure of the universe is a fundamental question in cosmology. Although the standard model usually assumes a trivial topology, a multiply connected universe can break statistical isotropy and generate off-diagonal covariance between the spherical-harmonic coefficients of cosmic microwave background fluctuations. In this work, we investigate whether CMB B-mode polarization improves constraints on the cubic three-torus, or $E_1$ topology. We construct the full harmonic-space covariance matrices of the temperature, E-mode, and primordial B-mode anisotropies, including correlations between different $(\\ell,m)$ modes, and evaluate Gaussian likelihoods using random realizations generated from a statistically isotropic $Λ$CDM model with trivial topology. To isolate the intrinsic topological information carried by each CMB observable, we consider the ideal cosmic-variance-limited case, neglecting instrumental noise and gravitational lensing. We find that adding primordial B-mode polarization yields only a marginal improvement in the ability to distinguish the $E_1$ topology from the trivial topology, even under these ideal conditions. The different constraining powers of the temperature, E-mode, and B-mode anisotropies can be understood through the combined effects of their transfer-function responses and the topology-induced off-diagonal correlations in harmonic space. }",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.05960",
  "author_total": 3,
  "authors": [
    {
      "name": "Ryota Himeno"
    },
    {
      "name": "Atsushi J. Nishizawa"
    },
    {
      "name": "Kiyotomo Ichiki"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7w8acrcj652kh.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.05960",
  "fulltext_url": null,
  "id": "7w8acrcj652kh",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.05960",
  "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",
      "astro-ph.CO"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7220657140",
  "pdf_url": "https://arxiv.org/pdf/2610.05960",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7w8acrcj652kh.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:50Z",
      "native_id": "2610.05960",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.05960"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    }
  ],
  "title": "Limited Impact of CMB B-mode Polarization on Constraints on Cosmic Topology",
  "title_text": "Limited Impact of CMB B-mode Polarization on Constraints on Cosmic Topology",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:50Z",
  "url": "https://research.draconitic.com/paper/7w8acrcj652kh",
  "venue": "arXiv",
  "versions": []
}