Gravitational quantum effects in the light of BICEP2 results

Abstract

Recently BICEP2 found that the vanishing of the tensor-to-scalar ratio $r$ is excluded at $7\sigma$ level, and its most likely value is $r=0.2^{+0.07}_{-0.05}$ at $1 \sigma$ level. This immediately causes a tension with the Planck constraint $r < 0.11$. In addition, it also implies that the inflaton (in single field slow-roll inflation) experienced a Planck excursion during inflation $\Delta\phi /M_{Pl} \geq {\cal{O}}(1)$, whereby the effective theory of inflation becomes questionable. In this brief report, we show that the inflationary paradigm is still robust, even after the quantum effects are taken into account. Moreover, these effects also help to relax the tension on the different values of $r$ given by BICEP2 and Planck.