{
  "abstract": "We study a cosmological scenario in which the Universe contains standard baryonic matter, radiation, and a single unified dark fluid, the umami Chaplygin gas, which accounts for both dark matter and dark energy with no separate dark-matter component. We first analyse the thermodynamic behaviour of the fluid and show that, unlike earlier Chaplygin-type models, its thermodynamic stability is conditional rather than global: stability holds only above a critical density $ρ_1=\\sqrt{|A/w|}$, the fluid reheats once this density is crossed, and a viable low-density regime requires $|w|<2$. Thermodynamic stability at the present epoch requires $|A|<|w|ρ_0^2$, a condition that is more easily met for $|w|>1$. We then constrain both the $|w|<1$ and $|w|>1$ cases with Type Ia supernovae, DESI DR2 baryon acoustic oscillations, cosmic-chronometer Hubble data and Planck 2018 distance priors through a Markov Chain Monte Carlo analysis. The $|w|<1$ case fits all four datasets well, with $w \\simeq -0.73$, $Ω_m^{\\rm eff} \\simeq 0.32$ and $H_0 \\simeq 66.8$ km s$^{-1}$ Mpc$^{-1}$. It is statistically comparable to flat $Λ$CDM, with $Δ{\\rm AIC}=-4.8$ and $Δ{\\rm BIC}=+0.6$. Its best-fit parameters violate the stability condition. The $|w|>1$ case with a Gaussian prior satisfies the condition but fits worse, with $Δ{\\rm AIC}\\simeq+66$ relative to $Λ$CDM. The best fit that obeys the condition exactly still has $Δ{\\rm AIC}\\simeq+50$. Finally, a linear perturbation analysis shows that the adiabatic sound speed turns negative at exactly the same critical density, triggering exponential small-scale growth at late times in the observationally preferred case. These results reveal a tension between a good fit to background data and the physical stability of the umami unified dark fluid.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.03697",
  "author_total": 2,
  "authors": [
    {
      "name": "Trishit Banerjee"
    },
    {
      "name": "Atreyee Biswas"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6em283qfj15pa.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.03697",
  "fulltext_url": null,
  "id": "6em283qfj15pa",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.03697",
  "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",
      "physics.gen-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.03697",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6em283qfj15pa.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T15:21:25Z",
      "native_id": "2611.03697",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.03697"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.gen-ph",
      "subfield": "general"
    }
  ],
  "title": "The Umami Chaplygin Gas as a Unified Dark Fluid: Observational Constraints, Perturbative and Thermodynamic Stability Analysis",
  "title_text": "The Umami Chaplygin Gas as a Unified Dark Fluid: Observational Constraints, Perturbative and Thermodynamic Stability Analysis",
  "type": "preprint",
  "updated_at": "2026-11-06T18:21:01Z",
  "url": "https://research.draconitic.com/paper/6em283qfj15pa",
  "venue": "arXiv",
  "versions": []
}