{
  "id": "1910.09881",
  "version": "v1",
  "published": "2019-10-22T10:37:54.000Z",
  "updated": "2019-10-22T10:37:54.000Z",
  "title": "Measuring the Hubble constant from the cooling of the CMB monopole",
  "authors": [
    "Maximilian H. Abitbol",
    "J. Colin Hill",
    "Jens Chluba"
  ],
  "categories": [
    "astro-ph.CO",
    "astro-ph.IM"
  ],
  "abstract": "The cosmic microwave background (CMB) monopole temperature evolves with the inverse of the cosmological scale factor, independent of many cosmological assumptions. With sufficient sensitivity, real-time cosmological observations could thus be used to measure the local expansion rate of the Universe using the cooling of the CMB. We forecast how well a CMB spectrometer could determine the Hubble constant via this method. The primary challenge of such a mission lies in the separation of Galactic and extra-Galactic foreground signals from the CMB at extremely high precision. However, overcoming these obstacles could potentially provide an independent, highly robust method to shed light on the current low-/high-$z$ Hubble tension. We find that a 3\\% measurement of the Hubble constant requires an effective sensitivity to the CMB monopole temperature of approximately $60~\\mathrm{pK \\sqrt{yr}}$ throughout a 10-year mission. This sensitivity would also enable high-precision measurements of the expected $\\Lambda$CDM spectral distortions, but remains futuristic at this stage.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-10-22T10:37:54.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "hubble constant",
      "cosmic microwave background",
      "cdm spectral distortions",
      "monopole temperature evolves",
      "cmb monopole temperature"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}