{
"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"
}
}
}