(adsbygoogle = window.adsbygoogle || []).push({}); "Gravity Quantized" along Thiemann lines (by Lewandowski's team)

http://arxiv.org/abs/1009.2445

Gravity quantized

Marcin Domagala, Kristina Giesel, Wojciech Kaminski, Jerzy Lewandowski

(Submitted on 13 Sep 2010)

"...'but we do not have quantum gravity.' This phrase is often used when analysis of a physical problem enters the regime in which quantum gravity effects should be taken into account. In fact, there are several models of the gravitational field coupled to (scalar) fields for which the quantization procedure can be completed using loop quantum gravity techniques. The model we present in this paper consist of thegravitational field coupled to a scalar field.The result has similar structure to the loop quantum cosmology models, except for that it involvesall the local degrees of freedombecause no symmetry reduction has been performed at the classical level."

I did not anticipate this paper and it shows a research current in LQG that is different from the program pursued by Rovelli, Freidel, Livine, Oriti and others. It is closer to Thomas Thiemann's program.

He has one of two or three major LQG books (Thiemann 2007 Canonical Quantum General Relativity). Also this year he started a new LQG-oriented research center at the University of Erlangen. Already he has a fair number of PhD students and postdocs who have come to Erlangen from other places.

This paper by Lewandowski et al gives a different view of LQG from what you see in Rovelli's April paper, a kind of status report and summary of results. http://arxiv.org/abs/1004.1780

I want to quote some passages and think about it. My first thought is that it probably does not represent a split, but separate advances that will merge back together further on down the road. This has happened before.

Lewandowski is one of the major figures in QG and has been a longtime co-author of many papers with Ashtekar, going back some 15 years I guess. He is a rigorous mathematician as well as physicist. Proves theorems. This is why I think I should pay close attention.

What L. is doing here is very conservative. No spinfoam. Pure Hamiltonian "canonical" approach. Conventional manifold in which the spin-networks of LQG are embedded. It's contrary to where I expected the field was going. So it proves that my perception was flawed. Lewandowski et al get, it seems to me, strong results. I will quote some of the paper later.

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# Gravity Quantized along Thiemann lines (by Lewandowski's team)

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