Supersymmetric vacua of mass-deformed M2-brane theory

We count the supersymmetric vacua of mass-deformed N=6 U(N)×U(N) Chern-Simons-matter theory by calculating the Witten index. When the Chern-Simons level k is 1, our result perfectly agrees with that from the gravity dual, given by partitions of N. For general k, our index generalizes partitions of N, including additional degrees. We also comment on non-relativistic superconformal theories constructed from this model.