A Note on Large N Thermal Free Energy in Supersymmetric Chern-Simons Vector Models

We compute the exact effective action for \cN=3 U(N)_k and \cN=4,6 U(N)_k\times U(N')_{-k} Chern-Simons theories with minimal matter content in the 't Hooft vector model limit under which N and k go to infinity holding N/k, N' fixed. We also extend this calculation to \cN=4,6 mass deformed case. We show those large N effective actions except mass-deformed \cN=6 case precisely reduce to that of \cN=2 U(N)_k Chern-Simons theory with one fundamental chiral field up to overall multiple factor. By using this result we argue the thermal free energy and self-duality of the \cN=3,4,6 Chern-Simons theories including the \cN=4 mass term reduce to those of the \cN=2 case under the limit.