Lack of Books on Loop Quantum Gravity (LQG)

[Mentat]

I was wondering, why are there no books on LQG?

For string/M- theory you have "The Elegant Universe", "Hyperspace", "Beyond Einstein", and numerous others.

But, for LQG, the closest I may have found (and I'm not even sure about this, since I just got the book, and haven't really started reading it yet) is a book that examines different courses taken in the past to reach a theory of Quantum Gravity (the book is called "Three Roads to Quantum Gravity", and is by Lee Smolin), and LQG is supposed to be one of them.

Nevertheless, there is no book (to my knowledge) that is specifically designed to explain Loop Quantum Gravity. Why is that?

 

[DamienVryce]

very good question i have a friend that asked me that question a couple of days ago if someone knows of one that would be very helpful

 

[selfAdjoint]

What about Smolin's "Three Roads to Quantum Gravity"?

 

[marcus]

We could write one.

 

[marcus]

I haven't ever looked at Smolin's "Three Roads to Quantum Gravity" but I respect Smolin so I suspect the book is a good one.


THE book on quantum gravity (graduate school level) is due to be published by Cambridge University Press and is available in draft form on line at the author's website and is called "Quantum Gravity"

It is 300 pages of which a large part of the first 100 pages is non-mathematical, explanatory, historical, philosophical, with just a few equations.

So although the book is overall technical at graduateschool level, there is a lot of interesting not-so-technical reading in it.

You get it by google with keywords "Carlo Rovelli" which gets you the author's homepage at University of Marseille and underneath Rovelli's photograph, down a ways, there is a link to the draft in PDF form.

There needs to be a book at high school/college level that covers the easier stuff in Rovelli's book, some history, some philosophy about our different concepts of space and time.

Also loop quantum cosmology (LQC as Martin Bojowald calls it) should be in the book because it seems to be making more progress than the full theory---LQC is simpler mathematically than the full theory because it starts out making assumptions of large-scale uniformity about space that radically simplify everything, the way the Friedmann equations are a simplification of the Einstein equation. LQC is the accessible place where a book like that could get into the subject. Removal of BB singularity, prediction of inflation without extra rigamarole, classical limit.

Well that's how I picture it. Who started this thread? mentat. Mentat maybe you have a different idea of how the book should be, how much equations, how much intuitive expl. by analogies instead of equations, how much illustrations of spinfoams and stuff, how much discussion of straight classical GR (which is the model for LQG so you would have to do at least a chapter on the plain unquantized Gen Rel I guess)

How do you picture it?

 

[Mentat]

Originally posted by selfAdjoint
What about Smolin's "Three Roads to Quantum Gravity"?

I mentioned that in my post, didn't I? I meant to.

Anyway, so far as I can tell, it's not directed at explaining the pros and cons of LQG, so much as examining all three approaches to QG that have been made in recent years.

 

[Mentat]

Originally posted by marcus
I haven't ever looked at Smolin's "Three Roads to Quantum Gravity" but I respect Smolin so I suspect the book is a good one.


THE book on quantum gravity (graduate school level) is due to be published by Cambridge University Press and is available in draft form on line at the author's website and is called "Quantum Gravity"

It is 300 pages of which a large part of the first 100 pages is non-mathematical, explanatory, historical, philosophical, with just a few equations.

So although the book is overall technical at graduateschool level, there is a lot of interesting not-so-technical reading in it.

You get it by google with keywords "Carlo Rovelli" which gets you the author's homepage at University of Marseille and underneath Rovelli's photograph, down a ways, there is a link to the draft in PDF form.

There needs to be a book at high school/college level that covers the easier stuff in Rovelli's book, some history, some philosophy about our different concepts of space and time.

Also loop quantum cosmology (LQC as Martin Bojowald calls it) should be in the book because it seems to be making more progress than the full theory---LQC is simpler mathematically than the full theory because it starts out making assumptions of large-scale uniformity about space that radically simplify everything, the way the Friedmann equations are a simplification of the Einstein equation. LQC is the accessible place where a book like that could get into the subject. Removal of BB singularity, prediction of inflation without extra rigamarole, classical limit.

Well that's how I picture it. Who started this thread? mentat. Mentat maybe you have a different idea of how the book should be, how much equations, how much intuitive expl. by analogies instead of equations, how much illustrations of spinfoams and stuff, how much discussion of straight classical GR (which is the model for LQG so you would have to do at least a chapter on the plain unquantized Gen Rel I guess)

How do you picture it?

I don't know, I just figured there'd be one in the style of "The Elegant Universe" (by Brian Green, on M-theory).

Anyway, I'm just as interested in a more technical exposition (Greene and Kaku's books were for everyone to understand), I just want an available book that explains the pros and cons of LQG as a theory of QG.

Oh, btw, the book is called "Quantum Gravity"? String theory is an attempt at Quantum Gravity too, isn't it? Will the book deal with just LQG or all the approaches for QG?

 

[Mentat]

Originally posted by marcus
We could write one.

Very cool.

PF really would have a dramatic effect on the world then .

 

[selfAdjoint]

Brian Green's book is just about unique in its clarity and appeal, combined with a genuine feel for the technical matters. It would be a real challenge to keep up to that standard in a popular book on quantum gravity. The other thing is that Green was writing in the flush of the great duality boost/M theory birth within stringy theory. I don't know if LQG is at a point where a popularization would be appropriate. The corresponding thing to duality would be either the firm explanation of the Immirzi parameter or a rigorous proof that the low energy limit is GR. Or both, of course, preferably from one theoretical innovation :=)

 

[marcus]

Originally posted by selfAdjoint
Brian Green's book is just about unique in its clarity and appeal, combined with a genuine feel for the technical matters. It would be a real challenge to keep up to that standard in a popular book on quantum gravity. The other thing is that Green was writing in the flush of the great duality boost/M theory birth within stringy theory. I don't know if LQG is at a point where a popularization would be appropriate. The corresponding thing to duality would be either the firm explanation of the Immirzi parameter or a rigorous proof that the low energy limit is GR. Or both, of course, preferably from one theoretical innovation :=)

chance favors the prepared mind, was that Pasteur?

I'd be inclined to look for descriptions of stable parts of the theory now, and try some clear explanations, without
waiting for all the pieces to fall in place. A large part of the
book would probably be useable---with re-writing in places---however things are resolved

what worries me is that both Smolin and Rovelli are good writers
and Ashtekar is not that bad either. the minute the time is ripe for a book these guys will have all their chops down
Or? Both of you Mentat and selfAdjoint have ideas, can either of you see a niche that is not most probably covered already?

 

[marcus]

Originally posted by Mentat


Oh, btw, the book is called "Quantum Gravity"? String theory is an attempt at Quantum Gravity too, isn't it? Will the book deal with just LQG or all the approaches for QG?

I think when you posted that question we were talking about Rovelli's book called "Quantum Gravity". While a book is still in draft form and in process of being written nothing is certain. It is supposed to be published by Cambridge U. P. Personally I expect it will be finished in a year or so and go to press maybe 2005, and be called "Quantum Gravity" then just as the draft is now. But no future event is certain.

Rovelli is a relativist (GR expert) and a science historian. He passionately believes that the way to proceed is to merge GR and QM the two great theories of the 20th C, and not to discard GR and replace it by some other explanation of how gravity works.
He quite clearly sees string/brane theories as NOT a quantization of the essential Gen Rel---a theory which describes and models gravity through the changing SHAPE of space itself. he thinks that GR and QM each have a separate concepts of spacetime which are fundamentally incompatible and only by learning from both and arriving at a fundamental change in our conception of spacetime-----by actually quantizing the theory of General Relativity---will real progress be made.

The string/brane approach does not try to do this, as relativists see the issue, and the loop approach (though it tries to do it) may not succeed---in which case one takes up where one left off, with what has been learned, and goes ahead.

John Archibald Wheeler and others had an earlier quantization of GR in the 1960s, and it is actually proving useful to the Loop people now. One reason disproportionately much progress is being made by the Loop people in cosmology is because of pre-Loop work by Wheeler and deWitt along those lines in the 1960s.
So there is some cumulative gain. The relativists have gotten much closer to really quantizing General Relativity in the past 10 years----and especially in cosmology are getting results (including matter, predicting inflation, overcoming the singularity, matching the classical or semiclassical limit away from the singularity)
I can provide links if anyone cares to read the articles. But cosmology uses a simplified model not the full model, so there is
still a lot to do despite clear and impressive progress.

Anyway when Rovelli sitting in his office in Rome or Marseille or speaking at a conference says "quantum gravity" he means quantum general relativity, not string. So his book is not much about string. That's just the GR people's perspective---the particle theorist of course have a different perspective

Enrique Alvarez is a string theorist, I gave a link earlier to his survey paper "Loops versus Strings" that he gave at a Hep
conference this summer to a Hep audience. I try to keep tabs on both perspectives. Alvarez paper is really good (for what it is) I think.

 

[jeff]

I actually didn't like greene's book because the analogies I thought were unnecessarily ornate and he spent too much time on calabi-yau manifolds and mirror symmetry (Though I'm not surprised because this was the area in which he'd made his most important contributions).

On the other hand, despite smolin's misleading comparisons of string theory with LQG, and the way that the problems faced by LQG are first mentioned near the end of the book, I'm more enthusiastic about "three roads.." than the elegant universe.

 

[Mentat]

Originally posted by selfAdjoint
Brian Green's book is just about unique in its clarity and appeal, combined with a genuine feel for the technical matters. It would be a real challenge to keep up to that standard in a popular book on quantum gravity. The other thing is that Green was writing in the flush of the great duality boost/M theory birth within stringy theory. I don't know if LQG is at a point where a popularization would be appropriate. The corresponding thing to duality would be either the firm explanation of the Immirzi parameter or a rigorous proof that the low energy limit is GR. Or both, of course, preferably from one theoretical innovation :=)

Greene's book was indeed extraordinary. As to that other point, about timing on popularizing a theory (when there is great excitement about it among scientists), I hadn't considered that before, but I completely agree.

Thanks for mentioning that, it really hadn't come to my mind (though I did know that Duality was really hot when Greene wrote his book).

 

[Mentat]

Originally posted by jeff
I actually didn't like greene's book because the analogies I thought were unnecessarily ornate and he spent too much time on calabi-yau manifolds and mirror symmetry (Though I'm not surprised because this was the area in which he'd made his most important contributions).

On the other hand, despite smolin's misleading comparisons of string theory with LQG, and the way that the problems faced by LQG are first mentioned near the end of the book, I'm more enthusiastic about "three roads.." than the elegant universe.

Did you happen to read Kaku's book (Hyperspace)?

 

[sol1]

Smolin's Math?

Three Roads to Matter formation

Jeff sort of insinuated that I would be ignored becuase of my apparent state of confusion and that I should ask simple questions to start out.

That's kind of hard to do with all the information here. What might seem comprehensible to him , might be a void in someone else. I like to do generalizations, because I believe with the concepts how would one really engage the complexity of the issues involved, without simplfying it first?

Loop there asked a question about Category Theory, and I relayed that I would be doing research. What does this mean, that since I don't know squat, becuase of the answer was not appropriate to loop?

Well my start was trying to understand how Smolin developed his logic.

http://www.superstringtheory.com/forum/metaboard/messages18/345.html

First principle is the idea of what can be found in expressison from the state of supersymmetry, and then through expansive phases, become the discrete structure we find in cooling?

How is the math found in expression to be detail as such, and how is the idea behind cognitive science found as a basis in mathematics.

http://superstringtheory.com/forum/dualboard/messages12/630.html

http://www.superstringtheory.com/forum/metaboard/messages18/307.html

http://www.superstringtheory.com/forum/metaboard/messages18/260.html

These are a few links to show it really is not that easy to find the next step, and we do not have people who can guide at every step. But to insinuate that we should go back to the beginning then indeed that is exactly what I have done:)

I would appreciate comments, as to the content and in would appreciate the honesty to any of what I posted.


http://superstringtheory.com/forum/partboard/messages17/120.html

This link is directly linked to the understanding of metric analogies.


http://superstringtheory.com/forum/extraboard/messages12/726.html

I hope I have given some evidence of what is taking place here that is sufficent to say, that the physics is being applied theoretically, although only in generalized way, and not with the maths that must follow.

sol1

 

[sol1]

Think of Metric Analogies

http://superstringtheory.com/forum/partboard/messages17/126.html

The distance of the quark to quark measure would have revealed the dimensional understanding of that distance(the gravity field)?

Sol

 

[sol1]

http://digerati.edge.org/3rd_culture/bios/smolin.html




"What is space and what is time? This is what the problem of quantum gravity is about. In general relativity, Einstein gave us not only a theory of gravity but a theory of what space and time are--a theory that overthrew the previous Newtonian conception of space and time. The problem of quantum gravity is how to combine the understanding of space and time we have from relativity theory with the quantum theory, which also tells us something essential and deep about nature."

http://digerati.edge.org/3rd_culture/bios/smolin.html

 

[sol1]

Loop Quantum Gravity

http://www.perimeterinstitute.ca/activities/seminarseries/alltalks.cfm?CurrentPage=4&SeminarID=162&SlideNumber=1

Conception and visualization must be deveoped so that we can understand the language developemnt. This is where I am at.

Critical density and the understandng of the Friedmann equation help to orientate the understanding of curvature. The intuitiveness with which we now undrstand expansitory modes, on a cosmolgical level has to be somehow understood on a quantum level for us to conisder the dynamical reality on the behavior of dimensional significance of string congregation, string field interpetation. This is all speculation to me.



http://www.superstringtheory.com/forum/relboard/messages20/262.html



http://superstringtheory.com/forum/bhboard/messages10/108.html



http://superstringtheory.com/forum/dualboard/messages5/114.html

Hope this helps orientate the view I have about the effect on a comological scale, and how it has been viewed on a quantum level. The dynamics here are geometrically considered.



http://superstringtheory.com/forum/geomboard/messages3/121.html

Sol

 

[sol1]

In a Gravity Field

http://www.superstringtheory.com/forum/relboard/messages19/105.html

 

[marcus]

Originally posted by sol1
http://www.perimeterinstitute.ca/activities/seminarseries/alltalks.cfm?CurrentPage=4&SeminarID=162&SlideNumber=1

Conception and visualization must be deveoped so that we can understand the language developemnt. This is where I am at.

...<snip>...

Sol

I suspect I have not way to help you in putting these various pieces of your vision together but I checked out one of the interesting-sounding links you gave and found it was a 14-slide
seminar talk by Jerzy Lewandowski!

My impression of him is cool/solid rigorous careful conservative (in a good sense)-----not apt to buy something, no matter how inspiring it sounded, unless he could tell exactly what it means.

Lewandowski is the fellow who noticed something questionable about Thomas Theimann's 1996-1998 version of the LQG Hamiltonian, raining on Thiemann's parade and sending him back to the drawing board. Rather than retard development in the field (as some people expected) this seems to have served more to keep the development, which has been plentiful since 1998, more on-track than it might otherwise have been. So as a Quantum Gravity watcher I have a lot of regard for Lewandowski---he represents an ability to be self-critical----to prune back unneeded or misdirected creativity.

I was glad to get the link you gave to Lewandowski's 24 June 2003 talk. It is a recent overview in brief of a whole sector----not spin foams but all of the canonical quantization of General Relativity work.

I notice that he will be giving one of the talks at this month's
"Loops meets Strings" symposium at Berlin. Appropriately enough Lewandowski's talk will be on the LQG Hamiltonian Constraint.
Am hoping that one of us can find the transcript of his upcoming symposium talk on web soon afterwards. Thanks for the link!