Multi-Natural Inflation in Supergravity and BICEP2
  We revisit the recently proposed multi-natural inflation and its realization
in supergravity in light of the BICEP2 results. Multi-natural inflation is a
single-field inflation model where the inflaton potential consists of multiple
sinusoidal functions, and it is known that a sizable running spectral index can
be generated, which relaxes the tension between the BICEP2 and the Planck
results. In this paper we show that multi-natural inflation can accommodate a
wide range of values of $(n_s, r)$, including the spectral index close to or
even above unity. This will be be favored if the tension is resolved by other
sources such as dark radiation, hot dark matter, or non-zero neutrino mass. We
also discuss the implications for the implementation in string theory.
