{
  "abstract": "Preheating transforms the coherent, low-entropy energy of the post-inflationary inflaton condensate into a far-from-equilibrium bath of field quanta, and is therefore an intrinsically irreversible process. We quantify that irreversibility directly, by computing the coarse-grained phase-space entropy of the field fluctuations from classical-statistical lattice simulations performed with CosmoLattice. For each field we reconstruct the mode occupation numbers $n_k$ and evaluate $S=\\sum_k[(1+n_k)\\ln(1+n_k)-n_k\\ln n_k]$, following its growth through the different stages of reheating in a self-consistently expanding Friedmann-Lemaître-Robertson-Walker background. We study three canonical models coupled to a daughter scalar $χ$ through $g^2ϕ^2χ^2$. We discuss the ultraviolet vacuum floor intrinsic to the lattice initial conditions and argue that the produced entropy $ΔS$ is the physically robust diagnostic. The phase-space entropy thus provides a compact, dynamical measure that cleanly separates the resonance-dominated, turbulence-dominated, and spinodal regimes of preheating. We couple this entropy production back into the expansion through the general relativistic entropic acceleration (GREA) framework, modifying the self-consistent scale-factor evolution of CosmoLattice to include the entropic force. The resulting acceleration tracks the heat (the energy transferred to particles) rather than the entropy itself: it is substantial in the tachyonic and quartic-turbulent cases, where an $\\mathcal{O}(1)$ fraction of the coherent energy fragments into radiation, but negligible in the resonant $m^2ϕ^2$ model despite its copious entropy production. The slow perturbative reheating that follows generates the bulk of the cosmic entropy ($S_0 \\sim10^{88}$) yet drives no appreciable acceleration and shuts off entirely at thermalization.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.20242",
  "author_total": 1,
  "authors": [
    {
      "name": "Juan Garcia-Bellido"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ajhm0d7qt1ezr.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.20242",
  "fulltext_url": null,
  "id": "ajhm0d7qt1ezr",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.20242",
  "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",
      "gr-qc"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.20242",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ajhm0d7qt1ezr.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:19Z",
      "native_id": "2609.20242",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.20242"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Entropy production during reheating after inflation and General Relativistic Entropic Acceleration",
  "title_text": "Entropy production during reheating after inflation and General Relativistic Entropic Acceleration",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:19Z",
  "url": "https://research.draconitic.com/paper/ajhm0d7qt1ezr",
  "venue": "arXiv",
  "versions": []
}