Geometrical Quantum Time in the $U(1)^3$ Model of Euclidean Quantum Gravity

TL;DR

This paper explores the emergence of a geometrical quantum notion of time in a simplified $U(1)^3$ model of Euclidean quantum gravity, deriving a Schrödinger-like equation from quantum constraints.

Contribution

It introduces a method to define and analyze quantum time within a loop quantum gravity-inspired model, providing insights into the quantum nature of time in gravity.

Findings

Discrete relative time evolution equation derived

Schrödinger-like equation obtained in the continuous limit

Quantum operator for time identified and analyzed

Abstract

Loop Quantum Gravity faces challenges in constructing a well-defined Hamiltonian constraint and understanding the quantum notion of time. In this paper these issues are studied by quantizing the $U(1)^3$ model, a simplified system exhibiting features similar to general relativity. By isolating a holonomy component within the Hamiltonian constraint, a discrete relative time evolution equation for quantum states is obtained. Then a Shr\"{o}dinger-like equation is derived in continuous limit. Thus the physical states solving this Shr\"{o}dinger-like equation can be written out. The emergence of the time parameter and its corresponding quantum operator are analyzed. It indicates the notion of a geometrical quantum time for quantum gravity.