Primordial non-Gaussianity in warm inflation using $\delta N$ formalism
  A $\delta N$ formalism is used to study the non-Gaussianity of the primordial
curvature perturbation on an uniform density hypersurfaces generated by the
warm inflation for the first time. After introducing the framework of the warm
inflation and the $\delta N$ formalism, we obtain an analytic expression for
the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in slow
roll approximation, and find that the $\delta N$ formalism gives a very good
result. We analyse the magnitude of $f_{NL}$ and compare our result with those
of the standard inflation. Then we discuss two concrete examples: the quartic
chaotic model and the hilltop model. The quartic potential model can again be
in very good agreement with the Planck results in the warm inflationary
scenario, and we give out the concrete results of how the nonlinear parameter
depends on the dissipation strength of the warm inflation and the amounts of
expansion. We find that the range of the nonlinear parameters in these two
cases are both well inside of the allowed region of Planck.
