Speaker
Description
The Page-Wootters framework introduces a covariant observable for a physical system, allowing it to serve as a time reference—a clock—to describe the dynamics of a system of interest. Within this framework, standard Schrödinger dynamics is recovered when the clock and system do not interact. However, interactions generally lead to time-nonlocal and potentially nonunitary dynamics. We show that these effects stem from the standard choice of clock observables. Specifically, we present an example where a generalized clock observable yields unitary dynamics, while the standard choice results in nonunitarity. We then establish conditions on the joint state of the clock and system that allow for generalized clock observables that ensure unitarity. Finally, we outline a method to construct such observables when they exist.
