Reconciliation of Planck and BICEP results with Excited Initial States
by
Amjad Ashoorioon(Uppsala U)
→
Europe/Stockholm
122:026
122:026
Description
The BICEP2 experiment has announced a signal for primordial gravity waves with tensor-to-scalar ratio r=0.2+0.07−0.05. There are two ways to reconcile this result with the latest Planck experiment One is by assuming that there is a considerable tilt of r, T_r, with a positive sign, T_r=dlnr/dlnk≳0.57+0.29−0.27 corresponding to a blue tilt for the tensor modes of order n_T≃0.53+0.29−0.27, 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/dlnk≃−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. 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^2ϕ^2) with the latest Planck result and BICEP2 results by accommodating either the blue tilt of r or the negative large running of n_S.
