Coherent spin-networks

TL;DR

This paper proposes a new class of coherent states for Loop Quantum Gravity, linking spin-network labels with geometric interpretations and demonstrating their semiclassical properties for large spins.

Contribution

It introduces a novel construction of coherent states in Loop Quantum Gravity using heat-kernels and spin-network labels, connecting them with SL(2,C) and Thiemann's states.

Findings

States reproduce superpositions of spin-networks with Livine-Speziale intertwiners

Weights on spins are Gaussian times a phase, matching previous proposals

States exhibit semiclassical behavior at large spins

Abstract

In this paper we discuss a proposal of coherent states for Loop Quantum Gravity. These states are labeled by a point in the phase space of General Relativity as captured by a spin-network graph. They are defined as the gauge invariant projection of a product over links of Hall's heat-kernels for the cotangent bundle of SU(2). The labels of the state are written in terms of two unit-vectors, a spin and an angle for each link of the graph. The heat-kernel time is chosen to be a function of the spin. These labels are the ones used in the Spin Foam setting and admit a clear geometric interpretation. Moreover, the set of labels per link can be written as an element of SL(2,C). Therefore, these states coincide with Thiemann's coherent states with the area operator as complexifier. We study the properties of semiclassicality of these states and show that, for large spins, they reproduce a superposition over spins of spin-networks with nodes labeled by Livine-Speziale coherent intertwiners. Moreover, the weight associated to spins on links turns out to be given by a Gaussian times a phase as originally proposed by Rovelli.