8.4 Homogeneous models
There are still several open areas in homogeneous models, which later can be extended to
- This has already been mentioned above. Isotropic models provide simpler
settings to analyze, e.g., the physical inner product [127, 162, 24], observables, different
interpretations of quantum aspects or the emergence of a classical world.
- Even in isotropic models effective equations have not yet been derived
completely. A general scheme exists, shown to be analogous to standard effective action
techniques , but it remains to be applied completely to quantum cosmology. This will then
lead to a complete set of correction terms and their ranges of validity and importance. Also
the question of whether an effective action for quantum cosmology exists and what its form is
can be addressed.
- Matter systems provide a rich source of diverse scenarios, but a full analysis
is yet to be done. This includes adding different kinds of fluids , fermions or anisotropy
parameters (shear term).