  The robustness properties of bipartite entanglement in systems of N bosons
distributed in M different modes are analyzed using a definition of
separability based on commuting algebras of observables, a natural choice when
dealing with identical particles. Within this framework, expressions for the
robustness and generalized robustness of entanglement can be explicitly given
for large classes of boson states: their entanglement content results in
general much more stable than that of distinguishable particles states. Using
these results, the geometrical structure of the space of N boson states can be
explicitly addressed.
