{
  "id": "2110.04226",
  "version": "v1",
  "published": "2021-10-08T16:25:18.000Z",
  "updated": "2021-10-08T16:25:18.000Z",
  "title": "A Cosmological Underdensity Does Not Solve the Hubble Tension",
  "authors": [
    "Sveva Castello",
    "Marcus Högås",
    "Edvard Mörtsell"
  ],
  "comment": "24 pages, 5 figures",
  "categories": [
    "astro-ph.CO",
    "gr-qc",
    "hep-th"
  ],
  "abstract": "A potential solution to the Hubble tension is the hypothesis that the Milky Way is located near the center of a matter underdensity. We model this scenario through the Lema\\^itre-Tolman-Bondi formalism with the inclusion of a cosmological constant ($\\Lambda$LTB) and consider a generalized Gaussian parametrization for the matter density profile. We constrain the underdensity and the background cosmology with a combination of data sets: the Pantheon Sample of type Ia supernovae (both the full catalogue and a redshift-binned version of it), a collection of baryon acoustic oscillations data points and the distance priors extracted from the latest Planck data release. The analysis with the binned supernovae suggests a preference for a $-13 \\%$ density drop with a size of approximately 300 Mpc, interestingly matching the prediction for the so-called KBC void already identified on the basis of independent analyses using galaxy distributions. The constraints obtained with the full Pantheon Sample are instead compatible with a homogeneous cosmology and we interpret this radically different result as a cautionary tale about the potential bias introduced by employing a binned supernova data set. We quantify the level of improvement on the Hubble tension by analyzing the constraints on the B-band absolute magnitude of the supernovae, which provides the calibration for the local measurements of $H_0$. Since no significant difference is observed with respect to an analogous fit performed with a standard $\\Lambda$CDM cosmology, we conclude that the potential presence of a local underdensity does not resolve the tension and does not significantly degrade current supernova constraints on $H_0$.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-10-08T16:25:18.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "hubble tension",
      "cosmological underdensity",
      "baryon acoustic oscillations data points",
      "significantly degrade current supernova constraints",
      "data set"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 24,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}