{
  "abstract": "If cosmic acceleration is driven by a positive cosmological constant, the universe approaches an eternally accelerating de Sitter state, whose interpretation in quantum gravity remains elusive. We develop a framework in which acceleration is instead a transient stage of dark-sector relaxation towards compositional equilibrium: matter and dark energy approach a stationary density ratio, eventually diluting like pressureless matter. Guided by linear response theory and Onsager's near-equilibrium regression hypothesis, we describe this evolution through a composition variable measuring departure from equilibrium. Extending constant fractional relaxation to the full background evolution yields the dark-energy equation of state $w=w_0a^{-n}$, where $n$ is the relaxation rate per e-fold of expansion. This history connects early dark-energy suppression, an upward phantom crossing and a density maximum to a pressureless scaling future. Using DESI DR2 BAO and Planck distance priors, with and without three alternative supernova compilations, we find a nominal $2.6$--$3.6σ$ preference for nonzero relaxation over constant $w$. The composition framework also motivates a constitutive prescription for linear perturbations that remains regular at phantom crossing. Near equilibrium, regular long-wavelength composition disturbances relax at the background rate to leading order, while small-scale fluctuations propagate as damped sound waves. We prove, however, that for separately conserved matter and dark energy, the pointwise constitutive relation cannot sustain a regular, gradient-stable negative-pressure branch throughout its full past evolution. We explore modifications of the pressure response and their consistency with neighbouring homogeneous histories, identifying requirements for extending the near-equilibrium description to the full cosmological evolution.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.13739",
  "author_total": 1,
  "authors": [
    {
      "name": "Gianmassimo Tasinato"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/aks8t3kvbshjv.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.13739",
  "fulltext_url": null,
  "id": "aks8t3kvbshjv",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.13739",
  "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",
      "astro-ph.CO"
    ],
    [
      "arxiv",
      "hep-th"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7221564858",
  "pdf_url": "https://arxiv.org/pdf/2610.13739",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-09",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/aks8t3kvbshjv.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:28:36Z",
      "native_id": "2610.13739",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.13739"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-th",
      "subfield": "high-energy"
    }
  ],
  "title": "Relaxation Dark Energy: Compositional Dynamics and the Future of Cosmic Acceleration",
  "title_text": "Relaxation Dark Energy: Compositional Dynamics and the Future of Cosmic Acceleration",
  "type": "preprint",
  "updated_at": "2026-10-30T12:28:36Z",
  "url": "https://research.draconitic.com/paper/aks8t3kvbshjv",
  "venue": "arXiv",
  "versions": []
}