{
  "id": "2506.16022",
  "version": "v1",
  "published": "2025-06-19T04:40:10.000Z",
  "updated": "2025-06-19T04:40:10.000Z",
  "title": "The Impact of $Ω_{m0}$ Prior Bias on Cosmological Parameter Estimation: Reconciling DESI DR2 BAO and Pantheon+ SNe Data Combination Results",
  "authors": [
    "Seokcheon Lee"
  ],
  "comment": "10 pages, 3 figures",
  "categories": [
    "astro-ph.CO"
  ],
  "abstract": "Recent cosmological parameter analyses combining DESI DR2 Baryon Acoustic Oscillation (BAO) data with external probes, such as Pantheon+ Supernovae (SNe) observations, have reported deviations of the dark energy equation-of-state parameters ($\\oo, \\oa$) from the standard $\\Lambda$CDM model predictions ($\\oo=-1, \\oa=0$). A notable aspect of these results is the role of $\\Omo$ prior information from SNe, which is known to exhibit tension with BAO-only constraints. In this study, we rigorously investigate this effect through a statistical analysis using 100 mock DESI DR2 BAO data realizations. We demonstrate that the strong degeneracy between $\\oo$, $\\oa$, and $\\Omo$ causes significant biases in the estimated dark energy parameters when the $\\Omo$ prior mean deviates from its true underlying value. Specifically, applying an $\\Omo$ prior mean of 0.33 (consistent with some SNe-only constraints) to mock data, assuming a true $\\Lambda$CDM universe ($\\Omo=0.30, \\oo=-1, \\oa=0$), yields biased estimates such as $\\oo \\approx -0.82 \\pm 0.06$ and $\\oa \\approx -0.82 \\pm 0.4$. This systematic shift, driven by the $\\Omo$ prior, moves the estimated parameters towards the non-$\\Lambda$CDM region, offering a qualitative resemblance to outcomes reported in current combined DESI DR2 BAO + Pantheon+ SNe analyses (e.g., $\\oo = -0.888^{+0.055}_{-0.064}$, $\\oa = -0.17 \\pm 0.46$). Our findings suggest that these observed non-$\\Lambda$CDM parameters may largely arise from statistical biases due to $\\Omo$ prior tensions between datasets. This study proposes a potential resolution to current cosmological tensions without necessarily invoking new physics.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2025-06-19T04:40:10.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "sne data combination results",
      "reconciling desi dr2 bao",
      "cosmological parameter estimation",
      "dr2 baryon acoustic",
      "dr2 bao data"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}