Does anybody here remember Kodama state?

[zwicky]

Greetings!

I was just reading a very interesting review about Loop Quantum gravity by L. Smolin entitled "Quantum Gravity with a positive cosmological constant"

http://arxiv.org/abs/hep-th/0209079

I know that maybe the review it is out of date, for example there is just a briefly comment about the Immirzi parameter. It seems like then things were very optimistic in LQG as can be seeing from the introduction of the article.
Particularly I was very intrigued by the Kodama State, as a semi-classical solution of the theory. What is the current status of that semiclassical solution in the moder context of spin foams?

z.

 

[marcus]

Greetings!

I was just reading a very interesting review about Loop Quantum gravity by L. Smolin entitled "Quantum Gravity with a positive cosmological constant"

http://arxiv.org/abs/hep-th/0209079

I know that maybe the review it is out of date, for example there is just a briefly comment about the Immirzi parameter. It seems like then things were very optimistic in LQG as can be seeing from the introduction of the article.
Particularly I was very intrigued by the Kodama State, as a semi-classical solution of the theory. What is the current status of that semiclassical solution in the moder context of spin foams?

z.

The Loop program centered around Ashtekar Rovelli and Thiemann has never had much to say about either Kodama or about energy-dependent speed of light. Or braid-matter, or cosmic natural selection. Those were things Smolin talked and wrote about.

For instance, I don't remember Rovelli ever saying "Kodama state". I assume he must have made some mention of it somewhere sometime---maybe Atyy knows of a Rovelli paper on Kodama state. But I can't think of one.

So in that sense, nothing has changed. In never was and still is not a feature of the main Loop program.

Smolin has not written much Loop research since 2008, or maybe earlier. The braid matter business didn't catch on with the Loop community---nor did the energy-dependent speed of light---nor did cosmic natural selection (universe breeding thru black holes). He's a brilliant creative guy, but Loopwise somewhat out on the margins.

If you are interested in Smolin's ideas (and you should be!) then read Smolin. If you are interested specifically in Loop, which is quite a different matter, then I'd say read
http://arxiv.org/abs/1012.4707
Loop Quantum Gravity: the First Twenty-five Years
It's an excellent survey and review written for non-specialists, to be published in a special QG issue of the journal CQG (Classical and Quantum Gravity)