  In this work we study the effects of the electromagnetic coupling in natural
inflation in a systematic manner using the Schwinger-Keldysh formalism. The
corresponding influence functional is evaluated to one-loop level. It can be
interpreted as due to a single stochastic force. The equation of motion of the
inflaton field is therefore given in the form of a Langevin equation. Lastly,
the two-point and the three-point correlation functions of the inflaton field
are worked out. They are related to the power spectrum and the nongaussianity
of the inflaton field, respectively.
