Gravitational wave signature in B-modes and the power in ΛCDM models on large and small scales
Abstract
The cosmic microwave background (CMB) angular power spectrum has a drop in power at low multipoles (large scales), which is in tension with the standard ΛCDM + power-law spectrum model. This deficit is exacerbated if there is a significant tensor contribution to the CMB power spectrum, as recently suggested by the BICEP2 results. We show that this deficit appears naturally in the axion monodromy inflation model, where the inflaton potential contains a gentle oscillation, thus generating an oscillating power spectrum with a suppression of power at large scales while still achieving enough e-foldings to solve the horizon problem. Using a combined data set of Planck, ACT, and SPT temperature data along with WMAP polarization data, we find a best-fit tensor-to-scalar ratio r=0.07^{+0.06}_{-0.03} in this model. The BICEP2 result r 0.2 is disfavored by the data at the 99% confidence level. We show further that this oscillating power spectrum will also suppress power on small-scales, alleviating the too-big-to-fail in dwarf galaxies. Conversely, if a large-field inflation model such as axion monodromy is responsible for the deficit of power at large and small scales, then the imprint of gravitational waves on the CMB should be observable by B-mode polarization experiments in the future.
- Publication:
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American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22530101M