%0 Journal Article
%T The Lyth Bound of Inflation with a Tilt
%A Juan Garcia-Bellido
%A Diederik Roest
%A Marco Scalisi
%A Ivonne Zavala
%J Physics
%D 2014
%I arXiv
%R 10.1103/PhysRevD.90.123539
%X We provide strong evidence for universality of the inflationary field range: given an accurate measurement of $(n_s,r)$, one can infer $\Delta \phi$ in a model-independent way in the sub-Planckian regime for a range of universality classes of inflationary models. Both the tensor-to-scalar ratio as well as the spectral tilt are essential for the field range. Given the Planck constraints on $n_s$, the Lyth bound is strengthened by two orders of magnitude: whereas the original bound gives a sub-Planckian field range for $r \lesssim 2 \cdot 10^{-3}$, we find that $n=0.96$ brings this down to $r \lesssim 2 \cdot 10^{-5}$.
%U http://arxiv.org/abs/1408.6839v2