SLOCC Invariants for Multipartite Mixed States
  We construct a nontrivial set of invariants for any multipartite mixed states under the SLOCC symmetry. These invariants are given by hyperdeterminants and independent from basis change. In particular, a family of d^2 invariants for arbitrary d-dimensional even partite mixed states are explicitly given. 
Naihuan Jing, Ming Li, Xianqing Li-Jost, Ting-Gui Zhang, Shao-Ming Fei
quant-ph