Sometimes I wonder if LQG is as much of a "failure" as string theory, with string theory inability to dimensionally reduce uniquely, and LQG unable to define hamiltonian constraint.(adsbygoogle = window.adsbygoogle || []).push({});

Recent paper

http://arxiv.org/abs/1005.1866

Large-spin asymptotics of Euclidean LQG flat-space wavefunctions

http://arxiv.org/PS_cache/arxiv/pdf/1005/1005.1866v1.pdf

Aleksandar Mikovic, Marko Vojinovic

(Submitted on 11 May 2010)

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.

on page 20 "The asymptotics is not of the type required for correct semiclassical limit"

Perhaps an entirely new approach is needed, one that starts with correct semiclassical limit and work backwords (and whose kinematics, volume and area operators may disagree with LQG)

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Recent paper: LQG fails to give correct semiclassical limit

**Physics Forums | Science Articles, Homework Help, Discussion**