{
  "id": "2304.07281",
  "version": "v1",
  "published": "2023-04-14T17:50:35.000Z",
  "updated": "2023-04-14T17:50:35.000Z",
  "title": "Sweeping Horndeski Canvas: New Growth-Rate Parameterization for Modified-Gravity Theories",
  "authors": [
    "Yuewei Wen",
    "Nhat-Minh Nguyen",
    "Dragan Huterer"
  ],
  "comment": "23 pages, 6 figures",
  "categories": [
    "astro-ph.CO",
    "gr-qc"
  ],
  "abstract": "We propose and numerically validate a new fitting formula that is sufficiently accurate to model the growth of structure in Horndeski theories of modified gravity for upcoming Stage IV and V large-scale structure surveys. Based on an analysis of more than 18,000 Horndeski models and adopting the popular parameterization of the growth rate $f(z) = \\Omega_{M}(z)^{\\gamma}$, we generalize the constant growth index $\\gamma$ to a two-parameter redshift-dependent quantity, $\\gamma(z)$, that more accurately fits these models. We demonstrate that the functional form $\\gamma(z)=\\gamma_0+\\gamma_1z^2 / (1+z)$ improves the median $\\chi^2$ of the fit to viable Horndeski models by a factor of $\\sim40$ relative to that of a constant $\\gamma$, and is sufficient to obtain unbiased results even for precise measurements expected in Stage IV and V surveys. Finally, we constrain the parameters of the new fitting formula using current cosmological data.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-04-14T17:50:35.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "sweeping horndeski canvas",
      "modified-gravity theories",
      "growth-rate parameterization",
      "horndeski models",
      "two-parameter redshift-dependent quantity"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 23,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}