{
  "abstract": "We show that the logotropic dark fluid, proposed as a single-fluid unification of dark matter and dark energy, is exactly dissipative unimodular gravity with pressureless matter and the logarithmic energy diffusion function $Q(a)=3A\\ln a+Q_{c}$. The correspondence is exact at the level of the homogeneous background, rather than asymptotic, and introduces no parameters beyond those already present in either description. It provides a dynamical reinterpretation of the logotropic temperature $A$, whose origin was left open in the original proposal: up to the expansion rate, $A$ is the rate at which energy is diffused from matter into the geometric sector, $\\dot Q=3AH$. The adiabatic sound speed of the effective fluid is $c_{s}^{2}=A/ρ$, where $ρ$ is the unimodular matter energy density, and reaches the speed of light at $a_{s}=a_{M}/2^{1/3}$; the matter energy density then vanishes and changes sign at $a_{M}$, which is precisely the scale factor at which the model is known to become phantom. Since $ρ$ coincides with the enthalpy density $ε+P$ of the logotropic fluid, the phantom branch is the branch on which the matter sector carries negative energy density and on which the apparent horizon entropy decreases. Finally, we show that a one-parameter saturating diffusion law removes these late-time pathologies while preserving the low-redshift phenomenology.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.21006",
  "author_total": 2,
  "authors": [
    {
      "name": "Miguel Cruz"
    },
    {
      "name": "Samuel Lepe"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5qywpn0d5yc4r.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.21006",
  "fulltext_url": null,
  "id": "5qywpn0d5yc4r",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.21006",
  "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",
      "gr-qc"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7213889109",
  "pdf_url": "https://arxiv.org/pdf/2609.21006",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-17",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5qywpn0d5yc4r.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:03Z",
      "native_id": "2609.21006",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.21006"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "The logotropic dark fluid as an energy diffusion in unimodular gravity",
  "title_text": "The logotropic dark fluid as an energy diffusion in unimodular gravity",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:03Z",
  "url": "https://research.draconitic.com/paper/5qywpn0d5yc4r",
  "venue": "arXiv",
  "versions": []
}