Abstract
The BICEP-2 team has reported the detection of primordial cosmic microwave background B-mode polarization, with hints of a suppression of power at large angular scales relative to smaller scales. Provided that the B-mode polarization is due to primordial gravitational waves, this might imply a blue tilt of the primordial gravitational wave spectrum. Such a tilt would be incompatible with standard inflationary models, although it was predicted some years ago in the context of a mechanism that thermally generates the primordial perturbations through a Hagedorn phase of string cosmology. The purpose of this note is to encourage greater scrutiny of the data with priors informed by a model that is immediately falsifiable, but which \textit{predicts} features that might be favoured by the data-- namely a blue tensor tilt with an induced and complimentary red tilt to the scalar spectrum, with a naturally large tensor to scalar ratio that relates to both.
Highlights
Uncertainties due to galactic dust foregrounds remain, it is a constructive exercise to work out the implications of presuming some part of the detected B-mode signal to be due to primordial gravitational waves
The BICEP-2 team recently announced the possible detection of primordial cosmic microwave background (CMB) B-mode polarization, seemingly implying a tensorto-scalar ratio of r 1⁄4 0.2 Æ 0.05 [1] were dust foregrounds to contribute negligibly
The BICEP-2 Collaboration’s analysis took nT 1⁄4 0 as a prior in its simulated data, we wish to ask whether a suppression of power in the BB angular power spectrum at large angular scales relative to smaller scales might be present in the data, in particular in the B2 × Keck cross correlation function at long wavelengths
Summary
Brandenberger, Robert H., Ali Nayeri, and Subodh P. "Closed string thermodynamics and a blue tensor spectrum." Physical Review D 90.6 (2014): 067301. Comments This article was originally published in Physical Review D, volume 90, issue 6, in 2014. DOI: 10.1103/ PhysRevD.90.067301 Copyright American Physical Society. This article is available at Chapman University Digital Commons: http://digitalcommons.chapman.edu/scs_articles/297
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