Big Rip theory

We certainly talk about pre-geometry, though there are many "pre"s you can consider. Without even going into strings or loops, or even any quantum aspects... just think of space-time from the POV of the action, where it is simply a (local) minimum.

Yes, "imaginary time" is another concept that expands our normal notions of space-time. It doesn't manifest itself as an extra dimension, but is a change in the nature of time itself... imaginary time is much like our three dimensions of space.The important point about imaginary time is that it lifts the notion of reality to the pre-concept of the action or Lagrangian (as I alluded to in my above post). I think a long thread on the significance of Lagrangians (and most importantly, what they are!!!) is long overdue. It would nicely tie in with Son Goku's The mathematization of theoretical physics