Ramond Sector Characters and N=2 Landau-Ginzburg Models

We give a direct proof of the new "product" expression for the Ramond sector characters of N=2 minimal models recently suggested by E. Witten. Our construction allows us to generalize these expressions to the D and E series of N=2 minimal models, as well as to other N=2 Kazama--Suzuki coset models such as $SU(N)\times SO(2(N-1))/SU(N-1)\times U(1)$. We verify that these expressions indeed coincide with the corresponding Landau--Ginzburg "elliptic genus", a certain topologically invariant twisted path integral with the effective Landau--Ginzburg action, which we obtain by using Witten's method. We indicate how our approach may be used to construct (or rule out) possible Landau--Ginzburg potentials for describing other N=2 superconformal theories.