{
  "id": "1912.00995",
  "version": "v1",
  "published": "2019-12-02T18:58:31.000Z",
  "updated": "2019-12-02T18:58:31.000Z",
  "title": "How much primordial tensor mode is allowed?",
  "authors": [
    "Moumita Aich",
    "Yin-Zhe Ma",
    "Wei-Ming Dai",
    "Jun-Qing Xia"
  ],
  "comment": "12 pages, 7 figures",
  "categories": [
    "astro-ph.CO"
  ],
  "abstract": "The presence of a significant amount of gravitational radiation in the early Universe affects the total energy density and hence the expansion rate in the early epoch. In this work, we develop a physical model to connect the parameter of relativistic degree of freedom $N_\\mathrm{eff}$ with the amplitude and shape of primordial tensor power spectrum, and use the CMB temperature and polarization data from {\\it Planck} and BICEP2/KECK Array, and the primordial deuterium measurement from damped Lyman-$\\alpha$ (DLA) systems to constrain this model. We find that with this extra relation $\\Delta N_{\\rm eff}(r,n_{\\rm t})$, the tensor-to-scalar ratio $r$ is constrained to be $r<0.07$ ($3\\sigma$ C.L.) and the tilt of tensor power spectrum is $n_\\mathrm{t}=-0.01\\pm 0.31$ ($1\\sigma$ C.L.) for {\\it Planck}+BICEP2+KECK+[D/H] data. This achieves a much tighter constraint on the tensor spectrum and provides a stringent test for cosmic inflation models. In addition, the current constraint on $N_{\\rm eff}=3.122 \\pm 0.171$ excludes the possibility of fourth neutrino species at more than $5\\sigma$ C.L.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-12-02T18:58:31.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "primordial tensor mode",
      "primordial tensor power spectrum",
      "total energy density",
      "primordial deuterium measurement",
      "cosmic inflation models"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}