The Lyth Bound of Inflation with a Tilt
  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 $r \lesssim 2 \cdot
10^{-5}$.
