title: Inflation with whip-shaped suppressed scalar power spectra.
abstract: Motivated by the idea that inflation occurs at the grand unified theory symmetry breaking scale, in this Letter we construct a new class of large field inflaton potentials where the inflaton starts with a power law potential; after an initial period of relatively fast roll that lasts until after a few e folds inside the horizon it transits to the attractor of the slow roll part of the potential with a lower power. Because of the initial fast roll stages of inflation, we find a suppression in scalar primordial power at large scales and at the same time the choice of the potential can provide us a tensor primordial spectrum with a high amplitude. This suppression in scalar power with a large tensor-to-scalar ratio helps us to reconcile the Planck and BICEP2 data in a single framework. We find that a transition from a cubic to quadratic form of inflaton potential generates an appropriate suppression in the power of the scalar primordial spectrum that provides a significant improvement in fit compared to the power law model when compared with Planck and BICEP2 data together. We calculate the extent of non-Gaussianity, specifically, the bispectrum for the best fit potential, and show that it is consistent with Planck bispectrum constraints.
authors.affiliation: Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea.
authors.forename: Dhiraj Kumar
authors.initials: DK
authors.lastname: Hazra
authors.affiliation: Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea and Department of Physics, POSTECH, Pohang, Gyeongbuk 790-784, Korea.
authors.forename: Arman
authors.initials: A
authors.lastname: Shafieloo
authors.affiliation: Université Sorbonne Paris Cité, Laboratoire APC-PCCP Université Paris Diderot 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13, France and Physics Department & LBNL, University of California, Berkeley, California 94720, USA.
authors.forename: George F
authors.initials: GF
authors.lastname: Smoot
authors.affiliation: Landau Institute for Theoretical Physics RAS, Moscow 119334, Russia.
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Starobinsky