In this review, we analyse different aspects concerning the possibility to separate a gravity-
matter system into a part which lives close to a quasi-classical state and a “small” quantum …

The idea that events obey a definite causal order is deeply rooted in our understanding of
the world and at the basis of the very notion of time. But where does causal order come from …

The aim of this paper is to provide a general introduction to the problem of time in quantum
gravity. This problem originates in the fundamental conflict between the way the concept …

The canonical approach to quantum gravity has been put on a firm mathematical foundation
in the recent decades. Even the quantum dynamics can be rigorously defined, however, due …

The coupling of the metric to an incoherent dust introduces into spacetime a privileged
dynamical reference frame and time foliation. The comoving coordinates of the dust particles …

The problem of the identification of the observable quantities in quantum gravity (or in any
diffeomorphism invariant quantum theory) is considered. The author recalls Einstein's' hole …

The curvature coordinates T, R of a Schwarzschild spacetime are turned into canonical
coordinates T (r), ssR (r) on the phase space of spherically symmetric black holes. The entire …

This book concerns the foundations of Quantum Gravity, in particular from a conceptual point
of view. It provides a self-contained introduction to this topic, resting on particular features of …

Roughly speaking, classical statistical physics is the branch of theoretical physics that aims
to account for the thermal behaviour of macroscopic bodies in terms of a classical …

The author argues that only by taking into account the quantum properties of the bodies that
form the reference frames, physical quantum operators can be defined in quantum gravity …