Non-Bunch-Davis initial state reconciles chaotic models with BICEP and Planck

The BICEP2 experiment has announced a signal for primordial gravity waves with tensor-to-scalar ratio r = 0.2(-0.05)(+0.07) [1]. There are two ways to reconcile this result with the latest Planck experiment [2]. One is by assuming that there is a considerable tilt of r, T-r, with a positive sign, T-r = d lnr/d lnk greater than or similar to 0.57(-0.27)(+0.29) corresponding to a blue tilt for the tensor modes of order n(T) similar or equal to 0.53(-0.27)(+0.29), assuming the Planck experiment best-fit value for tilt of scalar power spectrum n(S). The other possibility is to assume that there is a negative running in the scalar spectral index, dn(S)/d lnk similar or equal to -0.02 which pushes up the upper bound on r from 0.11 up to 0.26 in the Planck analysis assuming the existence of a tensor spectrum. Simple slow-roll models fail to provide such large values for T-r or negative runnings in n(S) [1]. In this note we show that a non-Bunch-Davies initial state for perturbations can provide a match between large field chaotic models (like m(2)phi(2)) with the latest Planck result [3] and BICEP2 results by accommodating either the blue tilt of r or the negative large running of n(S). (C) 2014 The Authors. Published by Elsevier B.V.