Generalized Slow Roll for Tensors

Abstract

The recent BICEP2 detection of degree scale CMB B-mode polarization, coupled with a deficit of observed power in large angle temperature anisotropy, suggest that the slow-roll parameter ${\epsilon }_H$, the fractional variation in the Hubble rate per efold, is both relatively large and may evolve from an even larger value on scales greater than the horizon at recombination. The relatively large tensor contribution implied also requires finite matching features in the tensor power spectrum for any scalar power spectrum feature proposed to explain anomalies in the temperature data. We extend the generalized slow-roll approach for computing power spectra, appropriate for such models where the slow-roll parameters vary, to tensor features where scalar features are large. This approach also generalizes the tensor-scalar consistency relation to be between the ratio of tensor and scalar sources and features in the two power spectra. Features in the tensor spectrum are generically suppressed by ${\epsilon }_H$ relative those in the scalar spectrum and by the smoothness of the Hubble rate, which must obey covariant conservation of energy, versus its derivatives. Their detection in near future CMB data would indicate a fast roll period of inflation where ${\epsilon }_H$ approaches order unity, allowed but not required by inflationary explanations of temperature anomalies.

7 pages, 2 figures

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Cited by in corpus (9)

• Generalized Slow Roll in the Unified Effective Field Theory of Inflation
• Polarization Predictions for Inflationary CMB Power Spectrum Features
• Running from Features: Optimized Evaluation of Inflationary Power Spectra
• Nonlinear Excitations in Inflationary Power Spectra
• Reconciling tensor and scalar observables in G-inflation
• Can power spectrum observations rule out slow-roll inflation?
• From Non-trivial Geometries to Power Spectra and Vice Versa
• Scale invariance of the primordial tensor power spectrum
• Cross-tests of CMB features in the primordial spectra