into the statistical nature of particle creation and backreaction processes actually have a role to play in the second direction, i.e.,

ii\) Quantum field theory as the semiclassical limit of quantum gravity. How good is modified Einstein’s theory with backreaction from quantum matter fields an approximation to quantum gravity? Under what conditions can the quantum dynamics of spacetime described by a wave function make the transition to the classical picture described by trajectories in superspace? We will use the paradigms of quantum open systems applied to Misner’s minisuperspace models to illustrate these ideas.

From Dissipation to Quantum Open Systems
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Speaking from the path traversed by one of us, one can identify a few critical nodes in the search for a pathway which connects i) particle creation as a dissipative processes to ii) backreaction and semiclassical gravity to iii) the statistical aspects in the issue of quantum to classical transition which underlies the relation of quantum gravity and semiclassical gravity. (See the Ph.D. thesis of Sinha 1991 for an overview of other major developments and references in these areas.) The (in-out) effective action formalism (Schwinger 1951, DeWitt 1964, 1975) was a correct start, because it gives the rate of particle 