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Observable gravitational waves from inflation with small field excursions

Hotchkiss, Shaun and Mazumdar, Anupam and Nadathur, Seshadri (2012) Observable gravitational waves from inflation with small field excursions. Journal of Cosmology and Astroparticle Physics, 2012 (2). ISSN 1475-7516

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Abstract

The detection of primordial gravitational waves, or tensor perturbations, would be regarded as compelling evidence for inflation. The canonical measure of this is the ratio of tensor to scalar perturbations, r. For single-field slow-roll models of inflation with small field excursions, the Lyth bound dictates that if the evolution of the slow-roll parameter epsilon is monotonic, the tensor-to-scalar ratio must be below observationally detectable levels. We describe how non-monotonic evolution of epsilon can evade the Lyth bound and generate observationally large r, even with small field excursions. This has consequences for the scalar power spectrum as it necessarily predicts an enhancement in the spectrum at very small scales and significant scale-dependent running at CMB scales. This effect has not been appropriately accounted for in previous analyses. We describe a mechanism that will generically produce the required behaviour in epsilon and give an example of this mechanism arising in a well-motivated small-field model. This model can produce r\geq0.05 while satisfying all current observational constraints.

Item Type: Article
Journal or Publication Title: Journal of Cosmology and Astroparticle Physics
Additional Information: 14 pages, 4 figures
Uncontrolled Keywords: gravitational waves and CMBR polarization ; inflation ; cosmological parameters from CMBR
Subjects: Q Science > QC Physics
Departments: Faculty of Science and Technology > Physics
ID Code: 55940
Deposited By: ep_importer_pure
Deposited On: 19 Jul 2012 16:39
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 20:44
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/55940

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