TY - JOUR
T1 - Killing the straw man
T2 - Does BICEP prove inflation at the GUT scale?
AU - Dent, James B.
AU - Krauss, Lawrence
AU - Mathur, Harsh
N1 - Funding Information:
We acknowledge discussions with Kate Jones-Smith and Paul J. Steinhardt at an early stage of this work, and we thank referees for pointing out a numerical error in our initial analysis which affected our conclusions. LMK was supported in part by DOE grant DE-SC0008016 .
PY - 2014/9/7
Y1 - 2014/9/7
N2 - The surprisingly large value of r, the ratio of power in tensor to scalar density perturbations in the CMB reported by the BICEP2 Collaboration, if confirmed, provides strong evidence for Inflation at the GUT scale. While the Inflationary signal remains the best motivated source, a large value of r alone would still allow for the possibility that a comparable gravitational wave background might result from a self ordering scalar field (SOSF) transition that takes place later at somewhat lower energy. We find that even without detailed considerations of the predicted BICEP signature of such a transition, simple existing limits on the isocurvature contribution to CMB anisotropies would definitively rule out a contribution of more than 5% to r ≈ 0.2. We also present a general relation for the allowed fractional SOSF contribution to r as a function of the ultimate measured value of r. These results point strongly not only to an inflationary origin of the BICEP2 signal, if confirmed, but also to the fact that if the GUT scale is of order 1016GeV then either the GUT transition happens before Inflation or the Inflationary transition and the GUT transition must be one and the same.
AB - The surprisingly large value of r, the ratio of power in tensor to scalar density perturbations in the CMB reported by the BICEP2 Collaboration, if confirmed, provides strong evidence for Inflation at the GUT scale. While the Inflationary signal remains the best motivated source, a large value of r alone would still allow for the possibility that a comparable gravitational wave background might result from a self ordering scalar field (SOSF) transition that takes place later at somewhat lower energy. We find that even without detailed considerations of the predicted BICEP signature of such a transition, simple existing limits on the isocurvature contribution to CMB anisotropies would definitively rule out a contribution of more than 5% to r ≈ 0.2. We also present a general relation for the allowed fractional SOSF contribution to r as a function of the ultimate measured value of r. These results point strongly not only to an inflationary origin of the BICEP2 signal, if confirmed, but also to the fact that if the GUT scale is of order 1016GeV then either the GUT transition happens before Inflation or the Inflationary transition and the GUT transition must be one and the same.
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U2 - 10.1016/j.physletb.2014.07.046
DO - 10.1016/j.physletb.2014.07.046
M3 - Article
AN - SCOPUS:84905216739
SN - 0370-2693
VL - 736
SP - 305
EP - 307
JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
ER -