Document Type
Article
Publication Date
9-7-2014
Abstract
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.
Language
English
Publication Title
Physics Letters Section B Nuclear Elementary Particle and High Energy Physics
Grant
DE-SC0008016
Rights
© 2014 The Authors. Published by Elsevier B.V. This is an Open Access work distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/3.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Recommended Citation
James B. Dent, Lawrence M. Krauss, Harsh Mathur, Killing the straw man: Does BICEP prove inflation at the GUT scale?, Physics Letters B, Volume 736, 2014, Pages 305-307, ISSN 0370-2693, https://doi.org/10.1016/j.physletb.2014.07.046.
Manuscript Version
Final Publisher Version