Thomas Thiemann has responded to some critics, with a new conspectus of LQG and his Master Constraint Program. Here is his abstract; note the comment on Helling et al.(adsbygoogle = window.adsbygoogle || []).push({});

hep-th/0608210

From: Thomas Thiemann [view email]

Date: Tue, 29 Aug 2006 19:05:37 GMT (82kb)

Loop Quantum Gravity: An Inside View

Authors: Thomas Thiemann

Comments: 58 pages, no figures

Report-no: AEI-2006-066

Subj-class: High Energy Physics - Theory; Mathematical Physics

This is a (relatively) non -- technical summary of the status of the quantum dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical evolution of the subject and why the results obtained so far are non -- trivial. The present text can be viewed in part as a response to an article by Nicolai, Peeters and Zamaklar [hep-th/0501114]. We also explain why certain no go conclusions drawn from a mathematically correct calculation in a recent paper by Helling et al [hep-th/0409182] are physically incorrect.

The Helling et al. paper is this:

hep-th/0409182

From: Robert C. Helling [view email]

Date: Fri, 17 Sep 2004 10:53:26 GMT (19kb)

String quantization: Fock vs. LQG Representations

Authors: Robert C. Helling, Giuseppe Policastro

Comments: 19 pages

Report-no: DAMTP-2004-93

We set up a unified framework to compare the quantization of the bosonic string in two approaches: One proposed by Thiemann, based on methods of loop quantum gravity, and the other using the usual Fock space quantization. Both yield a diffeomorphism invariant quantum theory. We discuss why there is no central charge in Thiemann's approach but a discontinuity characteristic for the loop approach to diffeomorphism invariant theories. Then we show the (un)physical consequences of this discontinuity in the example of the harmonic oscillators such as an unbounded energy spectrum. On the other hand, in the continuous Fock representation, the unitary operators for the diffeomorphisms have to be constructed using the method of Gupta and Bleuler representing the diffeomorphism group up to a phase given by the usual central charge.

And Robert Helling has replied to Thiemann's claim http://atdotde.blogspot.com/2006/08/re-re.html" [Broken].

Meanwhile Lubos Motl had a teardown of Thiemann's paper on his blog (I am not going to link to it)., which the physicist who blogs as Capitalist Imperialist Pig then showed to be false (the word "lie" comes up http://capitalistimperialistpig.blogspot.com/2006/08/feynmans-toe-and-motls-convenient.html" [Broken]. Lubos commented with a critique of pig's essay that was typical Lubos: off the point and ending with this sentence: "I would like to help you to avoid similar stupidities in the future, but I have not yet discovered a cure that would change a complete idiot into a reasonable person"

There is also discussion at Christine Dantas's blog, but I haven't been there yet.

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