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 …

This tutorial provides an overview on the theory of attosecond streaking, a pump-probe
scheme to extract timing information of ionization processes that has been widely used in …

In quantum theory it is possible to explain time, and dynamics, in terms of entanglement.
This is the timeless approach to time, which assumes that the universe is in a stationary …

The nature of time as emergent for a system by separating it from its environment has been
put forward by Page and Wootters [Phys. Rev. D 27, 2885 (1983) PRVDAQ 0556-2821 …

We propose a time-of-arrival operator in quantum mechanics by conditioning on a quantum
clock. This allows us to bypass some of the problems of previous proposals, and to obtain a …

Time continues to be an intriguing physical property in the modern era. On the one hand, we
have the classical and relativistic notion of time, where space and time have the same …

The free propagation in time of a normalisable wave packet is the oldest problem of
continuum quantum mechanics. Its motion from microscopic to macroscopic distance is the …

This article addresses topics regarding time measurements performed on quantum systems.
The motivation is linked to the advent of'attophysics' which makes feasible to follow the …

The principle of least action originates in the idea that, if nature has a purpose, it should
follow a minimum or critical path. This simple principle, and its variants and generalizations …

This paper examines the various arguments that have been put forward suggesting either
that time does not exist, or that it exists but its flow is not real. We argue that: 1. Time both …