Gravitational quantum effects in the light of BICEP2 results

Understand

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.