A New N=4 Membrane Action via Orbifold
  We propose a new Lagrangian describing N=4 superconformal field theory in three dimensions. This theory is believed to describe interacting field theory on the worldvolume of a M2-brane on an orbifold, and is obtained as a Z_2-quotient of the theory proposed by Bagger and Lambert. Despite unusual Chan-Paton structures, we can take Z_2-orbifold by using SU(2)\times SU(2) bifundamental representations. We also analyze the moduli space of this theory and found three branches. With an assumption of a broken U(1) symmetry, the moduli space is consistent with that of the D2-brane in the strong coupling limit of Type IIA string theory if the gauge group is O(4). Our action has manifest Z_2-symmetry exchanging two R^4/Z_2's in M-theory, and this suggests a new non-perturbative duality between a O2^{-}-brane on orbifold R^4/Z_2 and a O2^{-}-brane with D6-branes. 
Hiroyuki Fuji, Seiji Terashima and Masahito Yamazaki