Is Quantum Gravity Too Complex for Beginners?

[Chronos]

For those who are interested in QG, but find it a bit daunting [like me], here is a nice read:

http://www.arxiv.org/abs/hep-th/0601129
Loop and spin foam quantum gravity: a brief guide for beginners

 

[Kalimaa23]

Thanks for the link! Although I'm doing my research in String Theory, I really want to stay in touch with other approaches to Quantum Gravity. I'll read it through and share my thoughts later.

 

[marcus]

principle author, Hermann Nicolai, is a string theorist and also
director of the QG and unified theories section of Albert Einstein Institute at Golm which hosted Loops'05 conference last October. So he is a string theorist who is unusually knowledgeable about quantum gravity research.

I put a link to this article in the QG links thread

 

[grottolab]

in my real world, seeking ONE theory of everything is counterintuitive folly, the pursuit of perfection (or divinity?) driven by a need to "get back at those nuns" of our formative years. Years spent here and now and nower,etc. suggest infinite theories, even infinite causes for each of the everythings in THE multiverse(s). Maybe this spounge should keep her head underwater, and stop trying to erase physicists' chalkboards; but, why seek ONE explanation for ALL existence? Sister MaryElizabeth's explanation with fancy math?

 

[francesca]

For those who are interested in QG, but find it a bit daunting [like me], here is a nice read:

http://www.arxiv.org/abs/hep-th/0601129
Loop and spin foam quantum gravity: a brief guide for beginners

Achtung! This article of Nicolai is not a review of the current state of Loop Quantum Gravity. It is written by a person out of the research in canonical and covariant (spinfoam) loop quantum gravity, it has not been written for a pedagogical purpose, on the contrary it is mostly a list of criticisms to the theory, from somebody working in an alternative direction.

For what concerns the canonical formalism, the review is so lacking that at that time (5 years ago now) there was a strong replay by Thomas Thiemann, who posted this paper
Loop Quantum Gravity: An Inside View. Aug 2006. 58 pp.
Published in Lect.Notes Phys. 721 (2007) 185-263 http://arxiv.org/abs/hep-th/0608210"

For the covariant formalism, this review does not cover the current spinfoam theory at all, since this has been formulated basically around 2007 (of course you can find some basic notions of spinfoam theory, but I would advise more recent reviews because they are more likely to be free from the old errors in the theory).

Learning loops from Nicolai would be like learning strings from Smolin ...

Cheers,
frances

 

[marcus]

in my real world, seeking ONE theory of everything is counterintuitive folly, the pursuit of perfection (or divinity?) driven by a need to "get back at those nuns" of our formative years. Years spent here and now and nower,etc. suggest infinite theories, even infinite causes for each of the everythings in THE multiverse(s). Maybe this spounge should keep her head underwater, and stop trying to erase physicists' chalkboards; but, why seek ONE explanation for ALL existence? Sister MaryElizabeth's explanation with fancy math?

You accidentally put your post in the wrong thread. This [2006] thread was about Loop gravity.

Loop explicitly avoids aiming at at "theory of everything". It follows the time-honored strategy of incremental "one-thing-at-a-time" progress. In this case the focus is on one particular aspect of the world---its spacetime geometry (which we experience as gravity)--temporarily ignoring the different varieties and specific interactions of matter.

It was the String program that, at least at one time, claimed to attempt a "theory of everything".

But your concerns seem more properly in the area of general philosophy. We have a philosophy subforum.

 

[marcus]

Achtung!

For the covariant formalism, this review does not cover the current spinfoam theory at all, since this has been formulated basically around 2007 (of course you can find some basic notions of spinfoam theory, but I would advise more recent reviews because they are more likely to be free from the old errors in the theory).

You are right, of course. The covariant (spin foam) LQG has been completely reformulated starting around 2007. I don't think the revolution in LQG really stabilized until late in 2010.
So there is no alternative to learning it from the August 2011 version of Zakopane Lectures
http://arxiv.org/abs/1102.3660

But Hermann N. is a class act. I really like what I see from him. It was very constructive, as a prominent string theorist, for him to learn about Loop, and get Loop people to join his institute, and write an introduction to Lqg from the outside perspective. Since he is one of the most respected European string theorists, this could serve as a bridge, in 2006.

This was back when most stringsters were either pointedly ignoring Loop or saying "Crackpot!" and "String is the only game in town."

He didn't. He set up a "Strings meets Loops" workshop at his institute in 2003 and then hosted the first Loops conference there in 2005. He fostered respect and communication.
His approach has been shown to be right, historically, and he was alone when he set out on the road.

I am not questioning your comment on the 2006 Nicolai Peeters paper. You are right on target. But from a larger perspective this guy has made a really significant contribution to the quantum theory of spacetime geometry/gravitation.