What are the best introductory resources for learning Loop Quantum Gravity?

[marcus]

There were questions in a couple of threads about what books/papers/recorded lectures could serve to give a good introduction to LQG. I gathered some excerpts from Leucippus' posts and want to make a fresh start---trying to understand and to stay more focused on the central problem.

...I would like to learn the basic fundamentals of Loop Quantum Gravity as efficiently as possible. I'm currently 63 years old. I majored in Physics and Chemistry eons ago, and so I'm rusty on everything but can potentially get back parts I need relatively quickly. The main thing I'm looking for is an overview that basically gives the main concepts of Loop Quantum Gravity. Another thing that might also be useful would be a course outline or syllabus intended for students who are interested in focusing on Loop Quantum Gravity...

Personal note: I can handle some graduate level materials, but I would really appreciate anything at all that is in the undergraduate realm that would specifically apply to, or be useful for, entering into the study of Loop Quantum Gravity.

I'm looking for materials that will give me a good understanding of the basic ideas from which I can then expand...

So that's where I'm at right now. I'm just looking for a way to get best organized to gain a better understanding as efficiently as possible. What I'd like to gain is a "Bird's Eye View" of what it's all about, then I can know better where I need to zoom in and get my hands dirty in the details. ...

...Gambini and Pullin's book looks like a good place for me to start. I've been reading it online as a preview in Google Books. They preview quite a lot of it so just that preview will keep me busy for a while and when I'm ready for more details I'll try the library.

I also looked through the Introductory lectures to loop quantum gravity by Pietro Doná and Simone Speziale. Some of the stuff on knot theory is familiar to me. I recently took a course in topology and manifolds in n-dimensional space. So some aspects of it will be more readily accessible to me than others...
I'm definitely going with Gambini and Pullin's book for an introductory course that will probably take me the better part of a year to complete. So that looks like the best place to start.

I was actually looking at that book previously, but I thought I better ask here first in case there are other suggestions. This Gambini and Pullin's book does appear to be the best Introductory approach at the current time though...

In general terms this is not an unusual situation to be in. At the moment I'm not sure how to answer. What I hope to do is gradually add references that might fill the bill for someone who wants up-to-date, say 2009 or later, introductory material specifically to LQG (and I would include LQC and Spinfoam).

Some actual LQG researchers (e.g. Hellmann, Vidotto) are PF members and do occasionally post here, so if we are lucky we might get advice from them, or equally well-qualified people. In any event we can make the attempt.

 

[marcus]

...I'm just wondering if a non-technical discussion of loop gravity in only one to ten pages has ever been achieved?

I would love to have a nice concise and refined synopsis of the main ideas of LQG along with perhaps a well-organized outline of what types of topics are most required.
...

Hi Leucippus, as you pointed out, you were quoting a post of mine from a long ways back. I'm a little embarrassed by the naive optimism that comes out later. That was October 2003.

...Eventually there should be a non-technical description of loop gravity in only one to ten pages. Let's keep this thread going until we have one, or find one in the literature...

It's late here now. I'll see what I can find along those lines tomorrow.

 

[space_cadet]

This seems as good an opportunity as any to introduce a paper I have been working on, along with a collaborator, which is intended as a bare-bones intro to LQG. Since the paper is not quite complete yet, it hasn't been uploaded to arXiv. However, since people seem to show continued interest and a need for something like this - notwithstanding the several existing introductions, including the excellent one by Dona and Speziale - I've decided to take this project public.

The draft pdf is attached to this message.

The paper isn't quite "10 pages" long, but hopefully those seeking to understand LQG might find it useful. The completed version will eventually end up on arXiv.

 

[Demystifier]

The draft pdf is attached to this message.

The paper isn't quite "10 pages" long, but hopefully those seeking to understand LQG might find it useful. The completed version will eventually end up on arXiv.

Looks nice!

One technical question:
How do you make those orange (to-do-later) comments in LaTeX?

 

[space_cadet]

Looks nice!

Hopefully it reads nice too

One technical question:
How do you make those orange (to-do-later) comments in LaTeX?

Using the latex package "todonotes".

 

[Demystifier]

Hopefully it reads nice too

It certainly does.

Using the latex package "todonotes".

Thanks!

 

[marcus]

At least one of the authors (see page 23) is a fan of the best in English prose style--early 19th C--typifying lightness, wit, lucidity.
This monograph, at least at first sight, seems exactly what we were looking for! Happy voyaging with it to whatever is the proper conclusion!

 

[atyy]

This seems as good an opportunity as any to introduce a paper I have been working on, along with a collaborator, which is intended as a bare-bones intro to LQG. Since the paper is not quite complete yet, it hasn't been uploaded to arXiv. However, since people seem to show continued interest and a need for something like this - notwithstanding the several existing introductions, including the excellent one by Dona and Speziale - I've decided to take this project public.

The draft pdf is attached to this message.

The paper isn't quite "10 pages" long, but hopefully those seeking to understand LQG might find it useful. The completed version will eventually end up on arXiv.

Until LQG recovers classical general relativity, what is the point of LQG being "minimal" compared to string theory?

 

[Leucippus]

Thanks to Marcus for starting this thread.

And special thanks to Space Cadet for posting your introductory PDF.

I can even just print out your table of contents and use that for a nice organizing template.

Shamefully, I can see where I'm going to need to brush up on General Relativity and QFT. I'm somewhat familiar with the general ideas of both of these fields, but it appears that I'm going to need to have a working knowledge of the mathematics behind them. So I guess learning this prerequisite mathematics is going to keep me pretty busy for a while.

I almost hate to ask in fear of derailing the thread, but since GR and QFT are both prerequisites can anyone point to books that can help someone get up and running on those subjects relativity quickly? Assume an undergraduate level of entry.

Also at 63 years old, am I just kidding myself that I could ever catch up?

I know they say that its never too late, but surely there has to come a time when that saying no longer holds true. I'm pretty sure it's too late for me to consider going out for professional Ice Hockey, for example.

Can I learn the mathematics of GR and QFT side-by-side in a year in a meaningful way?

It appears that a solid working knowledge of these two subjects is going to be paramount to getting anywhere in LQG.

 

[atyy]

For GR, I liked Matthias Blau's notes http://www.blau.itp.unibe.ch/Lecturenotes.html, and for QFT David Tong's were pretty friendly http://www.damtp.cam.ac.uk/user/tong/qft.html .

Blau's GR notes are temporarily unavailable, so one could also try Woodhouse's https://people.maths.ox.ac.uk/nwoodh/ or Hamilton's http://casa.colorado.edu/~ajsh/phys5770_10/notes.html .

To supplement Tong's QFT notes, I found Srednicki's draft version of his book easy-going http://web.physics.ucsb.edu/~mark/qft.html .

 

[Leucippus]

For GR, I liked Matthias Blau's notes http://www.blau.itp.unibe.ch/Lecturenotes.html, and for QFT David Tong's were pretty friendly http://www.damtp.cam.ac.uk/user/tong/qft.html .

Blau's GR notes are temporarily unavailable, so one could also try Woodhouse's https://people.maths.ox.ac.uk/nwoodh/ or Hamilton's http://casa.colorado.edu/~ajsh/phys5770_10/notes.html .

To supplement Tong's QFT notes, I found Srednicki's draft version of his book easy-going http://web.physics.ucsb.edu/~mark/qft.html .

Thanks atyy,

I downloaded Woodhouse's lectures on both SR and GR. They book look great. He takes SR into some serious transformations right off the bat. So it won't hurt me to start in on his SR course to reacquaint myself with with vector transformations and lineal algebra. It looks like he takes all that for granted right off the bat in GR.

I also downloaded Hamliton's book on GR. That's really solid too. That's an actual book, not just lecture notes, and he too starts right off with SR which is a nice way for me to get a grip on entering into the more complex tensors of GR.

I also downloaded Srednicki's QFT book. Although in the preface of his book he says the following:

http://users.csonline.net/designer/images/eq.gif

The second one up from the bottom looks familiar.

What am I missing here?

 

[atyy]

The second one up from the bottom looks familiar.

What am I missing here?

Missing?

BTW, I'm a biology major who studied physics for fun. I started learning about LQG and string theory a few years ago when my physics friends all started talking about Smolin's TTWP, and I didn't understand any of their conversations. My knowledge is very superficial, just enough to understand physics bar talk.

 

[Leucippus]

Missing?

I majored in physics and chemistry when I was in college and none of those equations on his list look familiar to me. So I'm wondering what courses I missed.

I have no clue what these equations are. Here are my best guesses, and trust me, these are really lame guesses:

http://users.csonline.net/designer/images/eq1.gif

Equation #1 appears to be describing the derivative of sigma with respect to omega, but I have no clue what the sigma or omega represent. This derivative appears to be equal to the magnitude squared of some function that appears to depend upon to angles.

My guess would be that this has something to do with electromagnetic fields. But clearly I'm guessing and I don't recall ever seeing this particular relationship using this specific notation.

In what course would I have learned this equation?

http://users.csonline.net/designer/images/eq2.gif
http://users.csonline.net/designer/images/eq3.gif

Equations 2 and 3 both appear to be state equations representing the state of some systems. But again. I don't recognize these specific equations.

http://users.csonline.net/designer/images/eq4.gif

Equation #4 appears to be a solution to Schrodinger's wave equation. But I have no clue what it is the wave function of. Again, just guessing I would imagine it's a wave function of something simply like a hydrogen atom.

http://users.csonline.net/designer/images/eq5.gif

Equation #5 I have no clue. I would guess that the dotted q might represent the derivative of a dynamic charge? And that's a really wild guess just to take a stab at it.

http://users.csonline.net/designer/images/eq6.gif

Equation #6, again I'm clueless. I would guess that it might have something do to with a magnetic field. But again, that's just an intuitive hunch. I don't recognize the equation.

On second guess I'm thinking it could also be a Lorentz transformation equation?

You can tell I'm really guessing on these.


http://users.csonline.net/designer/images/eq7.gif

Finally something I recognize. At least I hope so. It appears to be relating Energy with momentum and mass. A Special Relativity relationship. I know I've worked with that equation before, but even so I can recall the precise details, but if I got back into it and worked with it again, I'm sure it would come flooding back.

http://users.csonline.net/designer/images/eq8.gif

Equation #8 appears to be making a statement about an electric field, so this appears to be associated with Maxwell's equations. I've worked with Maxwell's equations before too, so I could potentially regain that fairly quickly.

But for the most part this is all Greek to me.


I don't know. Maybe I should just stick with the barroom chatter. I might be too far behind in the math to do any serious work with this stuff.

 

[atyy]

1. scattering cross section
2. raising operator (see harmonic oscillator)
3. Clebsch-Gordon coeficients (see angular momentum)
4. time-evolution of observable (see Heisenberg picture)
5. definition of Hamiltonian in terms of Lagrangian
6. Lorentz transformation
7.
8. electric field in terms of the vector and scalar potential

 

[atyy]

There's a great quantum mechanics course by Balakrishnan on Youtube.

The operator treatment of the harmonic oscillator is in lecture 12

The Clebsch-Gordon coefficients are in lecture 17

The vector potential is in lecture 16

 

[Leucippus]

I might be too far behind the train at this point.

Maybe I should just give up and go fishing.

 

[Leucippus]

There's a great quantum mechanics course by Balakrishnan on Youtube.

The operator treatment of the harmonic oscillator is in lecture 12

The Clebsch-Gordon coefficients are in lecture 17

The vector potential is in lecture 16

Oh, that's cool.

I watch those!

I enjoy watching lectures. :)

 

[atyy]

Is the weather good for fishing?

LQG (in its original form) is based on the Hamiltonian or canonical formulation of general relativity. This has its roots in classical mechanics, and there's quantum version of it (which is why you'll always hear about the Hamiltonian operator in Balakrishnan's lectures). Anyway, that means a knowledge of classical Hamiltonian mechanics is very useful. It is essentially a reformulation of Newton's equations for systems in which energy is conserved. Tong has a description in the last part of http://www.damtp.cam.ac.uk/user/tong/dynamics.html

GR, as discovered by Einstein, is more in a form that is like Newton's second law. The first Hamiltonian formulation of GR was the ADM formulation http://en.wikipedia.org/wiki/ADM_formalism. Later Ashtekar found another Hamiltonian formulation http://en.wikipedia.org/wiki/Ashtekar_variables. LQG started from the Ashtekar variables.

If you want LQG bar talk, I recommend Wuthrich's thesis http://philosophyfaculty.ucsd.edu/faculty/wuthrich/pub/WuthrichChristianPhD2006Final.pdf .

BTW, string theory is the best candidate for a working theory of quantum gravity at the moment. In AdS/CFT there is a non-perturbative and background independent candidate formulation for quantum gravity in AdS spaces. It probably doesn't model our universe, but because it is (non-rigourously) the only working theory of quantum gravity in some universe, it is something anyone interested in quantum gravity should know. Furthermore string theory has calculated the black hole entropy, whereas there is no such calculation in LQG (that is undisputed). That does not mean that you as a non-professional sohuld not study LQG first, but it's something to bear in mind.

 

[Leucippus]

Is the weather good for fishing?

Not really. I'm more of the gardening type anyway. And it is getting close to gardening season here. So that's really what I should be doing with my time.

Furthermore string theory has calculated the black hole entropy, whereas there is no such calculation in LQG (that is undisputed). That does not mean that you as a non-professional sohuld not study LQG first, but it's something to bear in mind.

In the spirit of bar room chatter let me pass some stuff by you.

I heard that someone had discovered a relationship between the surface area of the event horizon of a black hole and the entropy contained by the black hole. I have no clue how that was done mathematically. Was that indeed done using string theory?

In any case, I found that result to be quite intriguing because I have some "theories" (or speculative uneducated guesses) concerning black holes, that I'd like to pass by some knowledgeable physicists.

Let's suppose a person falls into a black hole. There are two perspectives. One is the perspective of an outside observer watching the unfortunate victim falling into the hole. The other perspective is the person who is falling into the hole.

But what do they see?

Well, the observer outside the black hold sees the victim falling toward the black hole, but never really reaching the event horizon. Is that correct? The person will appear to be falling more and more slowly until they basically freeze forever at the horizon. So the person outside the black hole never actually see anyone fall into the black hole.

On the other hand, what does the person who's falling into the black hole see?

Well looking back out toward the universe the falling observer would see the universe behaving more and more rapidly. Right? Because for them time is slowing down. This means that they will see the universe "speeding up".

If they observe the universe carefully enough they would notice that super novas are popping off at a phenomenal rate as they fall toward the black hole. Time will slow down for them to the point where it's basically almost at a stand still by the time they reach the event horizon.

If that's true, then when they look out at the universe they must see the universe racing off into its future. They will see stars blowing up in galaxies at a phenomenal rate. The galaxies will even be going dark as their stars die off, and the galaxies will all be racing away from each other at an increasing speed. By the time the victim actually reaches the event horizon the universe will basically be "over". All of time will have passed for the external universe.

In fact, wouldn't the event horizon itself represent infinitely slow time passing for the victim who's falling into the black hole?

Will there be any time left for them to actually "pass through" the event horizon?

And if they did such a thing, wouldn't that actually represent negative time for them?

Wouldn't time stop at the event horizon where the acceleration due to gravity requires a speed greater than that of light to escape?

If so, does it even make sense to speak about the "inside" of a black hole?

Maybe the event horizon is all there is to a black hole and they have no interior at all. It just doesn't exist.

Have another beer, this is just barroom chat remember?

If you have objections to my ideas above, that's cool, I'll be glad to hear them. But for now, let's assume that the event horizon is the black hole. It has no singularity within. In fact it has no "within" at all.

The event horizon is the black hole, and this explains why the entire entropy of the black hole is contained on the event horizon (because that's all there is to it).

When I heard about LQG and defining a fabric of spacetime based on some sort of "spin networks" (whatever that is), I started to wonder if it might be possible that the fabric of spacetime itself is something real, and when compressed to a certain point it is actually forced into a spherical shape. And when it's in that shape it warps the fabric around it and it stays in that shape like a knot or kink in the fabric of spacetime.

So that's what I have on my mind. Maybe black holes have no inside at all. Maybe they are just spherical bubbles of the fabric of spacetime. And if you fall "onto" one, what actually happens is that you instantly become part of that sphere thus increasing its surface area. And there is no actual "hole" at all. It's just a warped bubble of spacetime that basically has no interior at all.

Trying to figure out what's going on in the "center" of a black hole may be a totally erroneous idea.

So that's why I'm interested in learning how to describe a black hole in terms of a spacetime fabric. But chances are that's never going to happen because I'm too far behind the learning curve to realistically catch up.

So maybe I'll just stick with gardening, and let the pros figure out the black holes.

By the way, thanks for all the cool links. This is far better than me trying to find this information on my own. I'll definitely be looking into this stuff. How far I'll get with it is yet to be discovered.

 

[atyy]

Hawking derived the black hole entropy in semi-classical gravity.

In string theory, there is a derivation from full quantum gravity of the entropy for a class of black holes called "extremal". There is, as far as I know, no comparable derivation in LQG.

There are several different attempts to calculate the entropy in LQG

LQG seems to have a calculation of the black hole entropy, but not from the full quantum theory, but a semiclassical one, somewhat like Hawkings. http://arxiv.org/abs/1204.5122

There are also attempts reviewed by http://arxiv.org/abs/1201.6102 , but I don't think any succeed fully.

String theory also has not calculated the black hole entropy for non-extremal black holes.

 

[Physics Monkey]

I would say that, via holographic duality, string theory has computed the entropy of non-extremal black holes.

Also, does Wuthrich's thesis really not mention holography?

 

[atyy]

I would say that, via holographic duality, string theory has computed the entropy of non-extremal black holes.

I had a vague feeling that this should be so, but couldn't think of anything concrete. What's a good reference?

Also, does Wuthrich's thesis really not mention holography?

I think he can be forgiven since the thesis was mainly about LQG, not string theory ...

 

[marcus]

This looks like it is going to turn out to be a valuable piece of work. Potentially useful to a lot of people.

This seems as good an opportunity as any to introduce a paper I have been working on, along with a collaborator, which is intended as a bare-bones intro to LQG. Since the paper is not quite complete yet, it hasn't been uploaded to arXiv. However, since people seem to show continued interest and a need for something like this - notwithstanding the several existing introductions, including the excellent one by Dona and Speziale - I've decided to take this project public.

The draft pdf is attached to this message.

The paper isn't quite "10 pages" long, but hopefully those seeking to understand LQG might find it useful. The completed version will eventually end up on arXiv.

Here is Space Cadet's draft intro to LQG brought up from his post #3

https://www.physicsforums.com/attachment.php?attachmentid=56469&d=1362642184

It explicitly says it's intended to "help lower the barrier" to entry in the field. The draft is still incomplete, with the authors' marginal notes reminding where paragraphs need to be added or enlarged.
Aside from some gaps like that the treatment is largely SELF-CONTAINED. Stuff you need to know is reviewed as it is needed. Stuff is clearly motivated. The conventional jargon and codewords that naturally build up and obscure any technical subject over time are concisely and skillfully explained. There's the immediate transparency in some sections that you get when something apparently complex is simply translated.
So it's remarkably well-written. And that means some people are going to be able to jump into the subject matter with considerable understanding without spending a lot of time on classical GR and QFT prerequisites. The authors know how to review just what is needed, in the way it is needed.
Good job. I hope they have it completed before long. It is already really useful and if completed would, I think, be enormously valuable.

 

[marcus]

A bit of humor: the title echoes a famous 12th Century book originally written in Arabic, called A Guide to the Perplexed.
And on page 23 some folks will hear an echo of the first sentence of a great English novel.
"It is a truth universally acknowledged, that..."

 

[Leucippus]

This looks like it is going to turn out to be a valuable piece of work. Potentially useful to a lot of people.


Here is Space Cadet's draft intro to LQG brought up from his post #3

https://www.physicsforums.com/attachment.php?attachmentid=56469&d=1362642184

It explicitly says it's intended to "help lower the barrier" to entry in the field. The draft is still incomplete, with the authors' marginal notes reminding where paragraphs need to be added or enlarged.
Aside from some gaps like that the treatment is largely SELF-CONTAINED. Stuff you need to know is reviewed as it is needed. Stuff is clearly motivated. The conventional jargon and codewords that naturally build up and obscure any technical subject over time are concisely and skillfully explained. There's the immediate transparency in some sections that you get when something apparently complex is simply translated.
So it's remarkably well-written. And that means some people are going to be able to jump into the subject matter with considerable understanding without spending a lot of time on classical GR and QFT prerequisites. The authors know how to review just what is needed, in the way it is needed.
Good job. I hope they have it completed before long. It is already really useful and if completed would, I think, be enormously valuable.

Yes I really appreciate Space_Cadet sharing this document.

I'm really far behind the curve. I need a whole lot of prerequisites going as far back as basic QM. But this paper is really pointing the way to precisely what I need to focus in on.

I really appreciate the first 11 references to other introductory materials too.

Plus the following is really nice as well:

From the paper:

"We will begin with a brief review of the history of the field of quantum gravity in the
remainder of this section. Following this we review some topics in General Relativity in
Section 2 and Quantum Field Theory in section 3, which hopefully fall into the \Goldilocks
zone", providing all the necessary basis for LQG, and nothing more."

I haven't delved into this yet, but it's nice to know that this paper is going to be as focused as possible. So it's going to serve me well as an outline of what to study.

Even though, in my case, most of my focus will be trying to catch up on the prerequisites of even these topics. But at least I'll know that I'm heading down the right highway.

I might write my own paper as I put together my studies aimed at people who are as far behind the curve as I am, so I can point the way toward even learning the prerequisites as efficiently as possible.

 

[atyy]

A bit of humor: the title echoes a famous 12th Century book originally written in Arabic, called A Guide to the Perplexed.
And on page 23 some folks will hear an echo of the first sentence of a great English novel.
"It is a truth universally acknowledged, that..."

I shall have to read both some day!

 

[Physics Monkey]

I think he can be forgiven since the thesis was mainly about LQG, not string theory ...

Yeah, definitely, didn't mean to imply that he was missing something. I am more just interested sociologically in what filters out and what outsiders see as the important or active parts of string theory.

 

[julian]

I've had a bit of a go on improving the wikipedia page for loop quantum gravity...still working on it...Also working on the Hamiltonian constraint and the Master constraint programme entries...

 

[space_cadet]

Many thanks to Marcus, Leucippus and others for their kind reviews of our paper. Just to make things clear, I'm Deepak.

A couple of points:

1. I used to post as "space_cadet" on physics.stackexchange.com ... until that ecosystem became severely imbalanced and I left for good. The content of some of my answers (to questions on physics.SE) have found their way into lqgbewil. Since that is, and has always been, my own work and I have never surrendered my right to reuse my answers in other places, I do not expect anybody to yell "plagiarism". But still, with the he world being what it is, it is better to clear the air before someone chooses to create a controversy where there is scope for none.

So if you run across excerpts from this paper on physics.SE in the form of answers posted by one "user346" - that's me. Here's one example. Another example is the "Criticisms of LQG" section, where the list of criticisms was culled from an answer to this particular question, by a well-known critic of all things NOT stringy in origin. The responses (in lqgbewil) to each of those criticisms, of course, are all mine :D


2. Any and all comments, criticisms and corrections are solicited and welcome. You can post them here or e-mail them to me or Sundance (addresses in the paper). Not being "experts", per se, there are bound to be several mistakes, typos and perhaps some outright incorrect statements. Your assistance in finding and eliminating those defects would be invaluable.

Thanks again for taking the time to read our work. If you find the paper a good read, keep in mind that "easy reading, is damn hard writing" (N. Hawthorne)

 

[martinbn]

Hi space_cadet, since you are open to any comments, I have some comments/questions. I haven't read it carefully, so I may have simplly missed things, but it seems that there is a jump to section 5. At least I didn't see how it is motivated from the previous parts. Also that part is very sketchy, I don't think (at this is probably just me) I could read it if I hadn't looked at say Rovelli's Zakopane lectures.

 

[space_cadet]

You're right. There is a bit of a jump. That's partially because of my desire to avoid unnecessarily duplicating content which has already been nicely covered elsewhere, and partially because of lack of ideas. lqgbewil is not meant to be entirely self-contained. Its purpose is to serve as an entry-point, for the "bewildered", into the LQG literature. It is hardly a replacement for Rovelli2011Zakopane!

 

[marcus]

It's great to have you here, Deepak! You have a gift for clear motivated explanatory writing. I hope you develop this ability and use it much more in future. I suspect the growth of scientific culture depends as much on clear reliable explanation as it does on frontier research.

I was amused and delighted by the Hawthorne quote. I did not know it. Reminded me of the down-home pungency of some of Mark Twain's remarks.

I hope you will be able to go to Loops 2013 in July and present this introductory treatment because that would emphasize to the scientists at the conference how crucial it is to overcome conceptual barriers and aid entry into the field.
http://www.perimeterinstitute.ca/conferences/loops-13
Today I noticed that the announced speakers list for Loops-13 has grown. It's hard to tell from what is still a partial list of speakers, with no talk titles, but I think the spirit being fostered by the organizers is ecumenical---joining with other QG research lines---building bridges. And I would say, from the look of it, that special emphasis is being placed on having younger researchers present their work. See what you think when you look the list over:
Ivan Agullo, DAMPT Cambridge

Abhay Ashtekar, Pennsylvania State University

Aurelien Barrau, Universite Joseph Fourier

Eugenio Bianchi, Perimeter Institute

Steve Carlip, University of California, Davis

Fay Dowker, Imperial College, London

Razvan Gurau, Université Paris-Sud

Viqar Husain, University of New Brunswick

Kirill Krasnov, University of Nottingham

Etera Livine, Ens de Lyon

Alejandro Perez, Centre de Physique Theorique

Vincent Rivasseau, Universite Paris-Sud XI Orsay

Carlo Rovelli, Le Centre de Physique Théorique

David Skinner, DAMPT Cambridge, IAS

More speakers to be announced.

 

[marcus]

For convenience, in case some readers have not yet downloaded the draft introduction to LQG by Deepak and Sundance, here is the link to post #3 of this thread:
https://www.physicsforums.com/showthread.php?p=4298307#post4298307

Deepak included a file of their 50-some page paper as an attachment to that post.

 

[space_cadet]

It's great to have you here, Deepak! You have a gift for clear motivated explanatory writing.

Thanks Marcus.

I suspect the growth of scientific culture depends as much on clear reliable explanation as it does on frontier research.

There won't be much of a culture is no one knows what the heck is going on, right? :-D

I was amused and delighted by the Hawthorne quote. I did not know it. Reminded me of the down-home pungency of some of Mark Twain's remarks.

BTW the line in the paper: "Its a truth universally acknowledged ..." is due to Sundance.

I hope you will be able to go to Loops 2013 in July and present this introductory treatment because that would emphasize to the scientists at the conference how crucial it is to overcome conceptual barriers and aid entry into the field.

Haha. Thanks. Walk into the lion's den, you mean? What do you take me for? David?

See what you think when you look the list over

Gurau and Rivasseau have worked on group field theory which provides the mathematical machinery needed to put Sundance's braid picture on a solid foundation. Carlip, Ashtekar and Rovelli are among the "elders". But other than Skinner and Carlip, I don't see any surprises. Dowker has worked on causal sets, Krasnov and Agullo on black hole entropy, Perez on spin-foams (and BHE), and Viqar straddles both strings and loops. The ones whose work is (IMO only!) significant and whose names I don't see are Matteo Smerlak, Hal Haggard, Frodden, Amit Ghosh, Christian Corda, and Mohammad Ansari among others. So that's what I think.

As for me being there, I don't have a job, an affiliation or funding. So as much as I would like to visit PI for the second time and dine on wine and cheese at the black hole bistro, it does not seem to be on the cards for me at the moment. But from your lips to God's ears, as they say!

 

[atyy]

GFT is related to the Sundance braid proposal?