Addressing the issue of non-unitarity in anisotropic quantum cosmology
  In the present work we show that the widely believed pathology of the non-unitarity of anisotropic quantum cosmological models cannot be a generic problem. We exhibit a non trivial example, a Bianchi-I model with an ultrarelativistic fluid, that has a well behaved time independent norm. We also show that a suitable operator ordering should produce time independent norms for the wave packets in the case of other more realistic fluids as well. 
Sridip Pal and Narayan Banerjee
gr-qc hep-th