Decoherence is a phenomenon that provides a part of the explanation of why quantum systems and classical systems behave differently.
What I understood from decoherence so far is that it requires time because it simply takes a (somehow very short) while for a large quantum system to transit to classical behaviours through decoherence.
Now, the status of time in quantum gravity is not clear, and it could very well occur that time is an emergent quantity. So I thought decoherence should occur at time scales where time has already emerged. Yet I found this assertion on www.decoherence.de
Decoherence explains also how the Schrödinger equation of general relativity (the Wheeler-DeWitt equation) may describe the appearance of time in spite of being time-less"
I would like to understand how can decoherence be active in the timeless domain of the Wheeler-deWitt equation to allow the emergence of time, as decoherence seems to require time itself to happen. (Handwaving arguments are OK, but references are welcome!)