Large-spin asymptotics of Euclidean LQG flat-space wavefunctions

TL;DR

This paper investigates the large-spin behavior of Euclidean Loop Quantum Gravity wavefunctions, revealing they asymptotically form a sum of Gaussian functions that do not produce the expected graviton propagator.

Contribution

It provides a detailed analysis of the large-spin asymptotics of Euclidean LQG wavefunctions, highlighting their Gaussian nature and limitations for reproducing graviton propagators.

Findings

Large-spin asymptotics are sums of Gaussian functions.

Gaussian functions do not yield the correct graviton propagator.

The analysis uses the Laplace method on spin-network amplitudes.

Abstract

We analyze the large-spin asymptotics of a class of spin-network wavefunctions of Euclidean Loop Quantum Gravity, which corresponds to a flat spacetime. A wavefunction from this class can be represented as a sum over the spins of an amplitude for a spin network whose graph is a composition of the the wavefunction spin network graph with the dual one-complex graph and the tetrahedron graphs for a triangulation of the spatial 3-manifold. This spin-network amplitude can be represented as a product of 6j symbols, which is then used to find the large-spin asymptotics of the wavefunction. By using the Laplace method we show that the large-spin asymptotics is given by a sum of Gaussian functions. However, these Gaussian functions are not of the type which gives the correct graviton propagator.