Troubles with quantum anisotropic cosmological models: loss of unitarity
  The anisotropic Bianchi I cosmological model coupled with perfect fluid is quantized in the minisuperspace. The perfect fluid is described by using the Schutz formalism which allows to attribute dynamical degrees of freedom to matter. It is shown that the resulting model is non-unitary. This breaks the equivalence between the many-worlds and dBB interpretations of quantum mechanics. 
F.G. Alvarenga, A.B. Batista, J.C. Fabris, S.V.B. Goncalves