Helical Phase Inflation
  We show that the quadratic inflation can be realized by the phase of a
complex field with helicoid potential. Remarkably, this helicoid potential can
be simply realized in minimal supergravity. The global $U(1)$ symmetry of the
K\"ahler potential introduces a flat direction and evades the $\eta$ problem
automatically. So such inflation is technically natural. The phase excursion is
super-Planckian as required by the Lyth bound, while the norm of the complex
field can be suppressed in the sub-Planckian region. This model resolves the
ultraviolet sensitive problem of the large field inflation, besides, it also
provides a new type of monodromy inflation in supersymmetric field theory with
consistent field stabilization.
