In isotropic models the results are similar, but already here one can see conceptual differences. Since the model is based on ADM variables, in particular using the metric and not triads, it is not clear what the additional sign factor , which is then introduced by hand, means geometrically. In loop quantum cosmology it arose naturally as an orientation of triads, even before its role in removing the classical singularity, to be discussed in Section 5.16, had been noticed. (The necessity of having both signs available is also reinforced independently by kinematical consistency considerations in the full theory .) In homogeneous models the situation is even more complicated since sign factors are still introduced by hand, but not all of them are removed by discrete gauge transformations as in Section 5.8 (see  as opposed to ). Those models are useful to illuminate possible effects, but they also demonstrate how new ambiguities, even with conceptual implications, arise if guidance from a full theory is lost.
In particular, the internal time dynamics is more ambiguous in those models and thus not usually considered. There are then only arguments that the singularity could be avoided through the boundedness of relevant operators , but those statements are not generic in anisotropic models  or even the full theory . Moreover, even if all curvature quantities could be shown to be bounded, the evolution could still stop (as happens classically where not any singularity is also a curvature singularity). The focus has shifted to an understanding of horizon dynamics in black hole collapse, where not all properties of the quantum representation may be crucial [190, 189, 192].
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