Reconstructing the Local Potential of Inflation with BICEP2 data
  We locally reconstruct the inflationary potential by using the current
constraints on $r$ and $n_{\rm s}$ from BICEP2 data. Assuming small and
negligible $\alpha_{\rm s}$, the inflationary potential is approximately linear
in $\Delta\phi\sim M_{\rm pl}$ range but becomes non-linear in $\Delta\phi\sim
10 M_{\rm pl}$ range. However if we vary the value of $\alpha_{\rm s}$ within
the range given by constraints from {\it Planck} measurement, the local
reconstruction is only valid in the range of $\Delta\phi\sim 0.4 M_{\rm pl}$,
which challenges the inflationary background from the point of view of
effective field theory. We show that, within the range of $\Delta \phi \sim 0.4
M_{\rm pl}$, the inflation potential can be precisely reconstructed. With the
current reconstruction, we show that $V(\phi) \sim \phi^{2}$ and $\phi^{3}$ are
consistent, while $\phi$ model is ruled out by $95\%$ confidence level of the
reconstructed range of potential. This sets up a strong limit of large-field
inflation models.
