{
  "abstract": "We reconstruct the late-time expansion history with a hierarchical Gaussian process (GP) that co-samples the kernel hyperparameters $(σ_f,l)$ together with $(\\Hzero,\\Om,\\Ok,ω_b h^2)$. The data are 37 cosmic-chronometer $H(z)$ points, DESI DR2 BAO, Planck 2018 compressed distance priors, and Pantheon+ supernovae, coupled by a Monte-Carlo effective likelihood. DESI's headline Chevallier--Polarski--Linder (CPL) preference at $2.8$--$4.2σ$ uses the full Planck likelihood; we do not reproduce or refute that result. On this compressed-CMB pipeline the baseline posterior is $w(z\\simeq 0)=-0.80^{+0.26}_{-0.23}$ (68\\%~C.L.), less than $1σ$ from $w=-1$, with $l=3.79^{+0.81}_{-1.12}$. A CPL fit on the same data improves nested $\\lcdm$ by only $Δχ^2\\sim 1$; Akaike's criterion prefers nested $\\lcdm$ ($Δ\\mathrm{AIC}\\simeq 3$), while BIC is quoted only as an indicative check for correlated supernovae. The reconstructed $f_{\\rm DE}=1$ lies inside the 68\\% band at every grid point with $z\\le 1.6$. Ablations that fix $(σ_f,l)$, drop SN or LRG1/2 BAO, replace the radial-basis kernel by a Matérn family, swap the SN catalogue (Union3, DES-Y5, DES-Dovekie), or nest a residual GP around $\\lcdm$ leave the median $w(0)$ within $\\lesssim 1σ$ of $-1$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2607.23593",
  "author_total": 3,
  "authors": [
    {
      "name": "Enkun Li"
    },
    {
      "name": "Yu-Hao Mu"
    },
    {
      "name": "Zhihuan Zhou"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3hqksxfr3hme5.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.23593",
  "fulltext_url": null,
  "id": "3hqksxfr3hme5",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.23593",
  "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"
    ],
    [
      "openalex",
      "3103|Cosmology and Gravitation Theories"
    ]
  ],
  "openalex": "W7171486381",
  "pdf_url": "https://arxiv.org/pdf/2607.23593",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-19",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3hqksxfr3hme5.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:19Z",
      "native_id": "2607.23593",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.23593"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    }
  ],
  "title": "Hierarchical Gaussian-process reconstruction of late-time expansion with DESI BAO and compressed Planck priors",
  "title_text": "Hierarchical Gaussian-process reconstruction of late-time expansion with DESI BAO and compressed Planck priors",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:19Z",
  "url": "https://research.draconitic.com/paper/3hqksxfr3hme5",
  "venue": "arXiv",
  "versions": []
}