CMB Constraints on Principal Components of the Inflaton Potential

TL;DR

This paper constrains the shape of the inflaton potential using CMB data by decomposing deviations into principal components, revealing potential features at specific scales and providing a faster likelihood method.

Contribution

It introduces a principal component approach to constrain inflaton potential deviations from CMB data and offers a significantly faster likelihood computation method.

Findings

Constraints on inflaton potential deviations at 100 Mpc and 300 Mpc scales.

Evidence for deviations around the 300 Mpc scale at ~10% level.

A new, faster likelihood method for WMAP7 data.

Abstract

We place functional constraints on the shape of the inflaton potential from the cosmic microwave background through a variant of the generalized slow roll approximation that allows large amplitude, rapidly changing deviations from scale-free conditions. Employing a principal component decomposition of the source function G'~3(V'/V)^2 - 2V''/V and keeping only those measured to better than 10% results in 5 nearly independent Gaussian constraints that maybe used to test any single-field inflationary model where such deviations are expected. The first component implies < 3% variations at the 100 Mpc scale. One component shows a 95% CL preference for deviations around the 300 Mpc scale at the ~10% level but the global significance is reduced considering the 5 components examined. This deviation also requires a change in the cold dark matter density which in a flat LCDM model is disfavored by current supernova and Hubble constant data and can be tested with future polarization or high multipole temperature data. Its impact resembles a local running of the tilt from multipoles 30-800 but is only marginally consistent with a constant running beyond this range. For this analysis, we have implemented a ~40x faster WMAP7 likelihood method which we have made publicly available.