{
  "abstract": "Swimming microorganisms accumulate at boundaries, but the spatial statistics of the resulting layers are rarely measured. We report a population of colonial green algae, of order 71 $μ$m across, that accumulates against the rigid upper wall of a closed 1-2 mm chamber and holds a two-dimensional non-contacting arrangement for about 105 min. The pair correlation function has a first shell at $r/\\bar{D} = 1.73$, $g = 4.8$; a hard-disc null at the same area fraction reaches only $g = 2.1$, so the ordering is not excluded volume alone. Nearest-neighbour separation is $1.80 \\pm 0.13$ diameters. The bond-orientational order parameter is $\\langle|ψ_6|\\rangle = 0.456$ against 0.385 for the null, only 36% of interior colonies are six-coordinated, and the orientational correlation $g_6(r)$ decays over 1.5 diameters with $η_6 = 1.31$ against the hexatic bound of 1/4: the arrangement is a two-dimensional liquid, not a crystal or a hexatic. Colonies execute a persistent random walk with reorientation time 1.4-1.7 s at Reynolds number $\\sim 9\\times 10^{-4}$. Breakup begins at 127 min. Thermal convection is excluded on Rayleigh-number grounds. Caveats: the length calibration is nominal rather than metrological, and this is a single population observed once. All data and code are deposited.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.09946",
  "author_total": 1,
  "authors": [
    {
      "name": "Nicholas Tufillaro"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/avkn75fdnf1ds.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.09946",
  "fulltext_url": null,
  "id": "avkn75fdnf1ds",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.09946",
  "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",
      "cond-mat.soft"
    ],
    [
      "arxiv",
      "nlin.AO"
    ],
    [
      "arxiv",
      "physics.bio-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.09946",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/avkn75fdnf1ds.ris",
  "sources": [
    {
      "first_seen": "2026-11-10T06:21:23Z",
      "native_id": "2611.09946",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.09946"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.bio-ph",
      "subfield": "biological-medical"
    },
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.soft",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:nlin.AO",
      "subfield": "statistical-nonlinear"
    }
  ],
  "title": "Two-dimensional liquid-like order in a confined population of swimming Eudorina colonies",
  "title_text": "Two-dimensional liquid-like order in a confined population of swimming Eudorina colonies",
  "type": "preprint",
  "updated_at": "2026-11-10T06:21:23Z",
  "url": "https://research.draconitic.com/paper/avkn75fdnf1ds",
  "venue": "arXiv",
  "versions": []
}