Bridging Quantum and Semiclassical Volume: A Numerical Study of Coherent State Matrix Elements in Loop Quantum Gravity

TL;DR

This paper develops a numerical algorithm to compute the volume operator's quantum action in Loop Quantum Gravity, validating it against analytical results and exploring quantum-classical connections.

Contribution

It introduces a generalized numerical method for volume operator calculations on spin-network states, bridging quantum and semiclassical regimes.

Findings

Numerical results match analytical expectations in the semiclassical limit.

Maximal eigenvalues approach classical polyhedral volumes.

Volume magnitudes vary significantly in the deep quantum regime for irregular geometries.

Abstract

In Loop Quantum Gravity, the quantum action of the volume operator is crucial in understanding quantum dynamics. In this work, we implement a generalized numerical algorithm that can compute the quantum action of the volume operator on a broad class of gauge-variant and gauge-invariant spin-network states. This algorithm is later used to calculate the coherent state expectation value and coherent state matrix elements of the volume operator. By comparing the results generated by our numerical model with the analytical results in various scenarios at the near-semiclassical region, not only is our numerical model validated with high accuracy, but it also provides a complete picture of how the full quantum action of the volume operator connects with its semiclassical approximations. We further find that the maximal eigenvalue approaches the classical polyhedral volume in the semiclassical regime. For irregular geometries, we also observe that the relative volume magnitudes can change in the deep quantum regime.