Bipartite entanglement in systems of identical particles: the partial   transposition criterion
  We study bipartite entanglement in systems of N identical bosons distributed in M different modes. For such systems, a definition of separability not related to any a priori Hilbert space tensor product structure is needed and can be given in terms of commuting subalgebras of observables. Using this generalized notion of separability, we classify the states for which partial transposition turns out to be a necessary and sufficient condition for entanglement detection. 
F. Benatti, R. Floreanini, U. Marzolino
quant-ph cond-mat.other hep-th