Natural Chaotic Inflation and UV Sensitivity
  If the recent measurement of B-mode polarization by BICEP2 is due to
primordial gravitational waves, it implies that inflation was driven by energy
densities at the GUT scale $M_{GUT} \sim 2\times 10^{16} GeV$. This favors
single-field chaotic inflation models. These models require transplanckian
excursions of the inflaton, forcing one to address the UV completion of the
theory. We use a benchmark 4d effective field theory of axion-4-form inflation
to argue that inflation driven by a quadratic potential (with small
corrections) is well motivated in the context of high-scale string theory
models; that it presents an interesting incitement for string model building;
and the dynamics of the UV completion can have observable consequences.
