Smolin video LQG online course

[marcus]

I've been watching Lecture #15.
it seems like the best yet
he's quantizing the classical theory and making a hilbert space etc.
giving intuition that had not come to me before

has anybody else been watching #15?
anybody else find it helpful too?

dynamics comes next week (#17,18)

Oriti just walked in, at the moment I was watching lecture #15

Oriti is supposed to give lecture #19 maybe also #20
because they get to spinfoam at that point

===================
BTW I've been learning to use the "slide list" menu option in sonicfoundry mediasite streamers

so I can watch particular parts of a lecture----or come back to where I had to stop the day before

if you are watching #15, well it has 64 slides
and a particularly cool part is right around slide 61 or 62
so suppose you want to go to that slide and start the whole thing there (instead of starting at the beginning)

you go to the slide list and you see numbers 1,2,...,7

each one of those baskets 1,...6 holds 10 slides
so they hold the first 60 slides
you click on 7 and you see thumbnails of slides 61,...,64
and you see which one you want and you click on "start from slide"
and it starts playing from that slide

has anyone else been using this feature? it really ups the efficiency of the whole process of watching

 

[Mike2]

I've been watching Lecture #15.
it seems like the best yet
he's quantizing the classical theory and making a hilbert space etc.
giving intuition that had not come to me before

What would really be cool is if someone would give a brief one paragraph summary of what will be covered in each part and even include some reference as to what course material will be covered.

 

[selfAdjoint]

What would really be cool is if someone would give a brief one paragraph summary of what will be covered in each part and even include some reference as to what course material will be covered.

Check out Christine Dantas' "The Hand of a Master" series of posts at http://christinedantas.blogspot.com/, She is doing just that, and she's up to Parts 5 and 6.

 

[Mike2]

Check out Christine Dantas' "The Hand of a Master" series of posts at http://christinedantas.blogspot.com/, She is doing just that, and she's up to Parts 5 and 6.

Thanks selfAdjoint.
It is also mentioned that one of the books used as reference is:
Gauge Fields, Knots, and Gravity (Series on Knots and Everything, Vol. 4) (Paperback)
by John C. Baez, Javier P. Muniain
at: https://www.amazon.com/gp/product/9810220340/?tag=pfamazon01-20

It is $500.00 each.

I wonder if the followning book might contain the same material:
Loops, Knots, Gauge Theories and Quantum Gravity (Paperback)
by Rodolfo Gambini
at: https://www.amazon.com/gp/product/0521654750/?tag=pfamazon01-20

 

[selfAdjoint]

Thanks selfAdjoint.
It is also mentioned that one of the books used as reference is:
Gauge Fields, Knots, and Gravity (Series on Knots and Everything, Vol. 4) (Paperback)
by John C. Baez, Javier P. Muniain
at: https://www.amazon.com/gp/product/9810220340/?tag=pfamazon01-20

It is $500.00 each.

I wonder if the followning book might contain the same material:
Loops, Knots, Gauge Theories and Quantum Gravity (Paperback)
by Rodolfo Gambini
at: https://www.amazon.com/gp/product/0521654750/?tag=pfamazon01-20

Yep, we all found out about that price for the Baez-Munian book It's because it is out of print and very much in demand. There is supposed to be a new edition coming out, but nobody knows when. I don't know the answer to your question about the Gambini book, sorry. Maybe Baez can tell us? He does check in here every now and then.

 

[marcus]

#17 and #18 of the Smolin Lectures are on line
(Hamiltonian constraint, area and volume operators)

this is from 22 March

on 29, next wednesday, Daniele Oriti will give the lecture, on spinfoam models (will have a review of Feynman diagrams)

the next week, 5 April, Viqar Hussain on black holes and elimating singularities

 

[Mike2]

Yep, we all found out about that price for the Baez-Munian book It's because it is out of print and very much in demand. There is supposed to be a new edition coming out, but nobody knows when. I don't know the answer to your question about the Gambini book, sorry. Maybe Baez can tell us? He does check in here every now and then.

I bought Rovelli's book, Quantum Gravity
at: https://www.amazon.com/gp/product/0521837332/?tag=pfamazon01-20
I was hoping it would help me with Smolin's video course. But chapter two of Rovelli's book starts out too dense for me. I'm getting lost in the indicies. Does anyone know a good primer for this notation he uses for GR? Thanks.

 

[garrett]

For a large and excellent treatment of GR, including index gymnastics, Wald is my favorite:
http://tinyurl.com/zs3u5

For a concise but thorough (and dense) online treatment, I like Peldan's review:
http://xxx.lanl.gov/abs/gr-qc/9305011

Indices are a bit like spoons in The Matrix... when you get really good at using and fully understanding them, there are no indices.

 

[rtharbaugh1]

Hi Mike2

I've been trying to get the indice idea from Baez on GR at

http://math.ucr.edu/home/baez/gr/outline2.html

but still getting stuck.

Thanks, Garret, for additional resources. I'll take a look at those.

R.

 

[rtharbaugh1]

#17 and #18 of the Smolin Lectures are on line
(Hamiltonian constraint, area and volume operators)

this is from 22 March

on 29, next wednesday, Daniele Oriti will give the lecture, on spinfoam models (will have a review of Feynman diagrams)

the next week, 5 April, Viqar Hussain on black holes and elimating singularities

Will this be broadcast in realtime? If so, what time CST? And how do I access it? I don't see it listed at the Mediasite link.

R.

 

[marcus]

Will this be broadcast in realtime? If so, what time CST? And how do I access it? I don't see it listed at the Mediasite link.

R.

I can't tell the future obviously but Oriti is scheduled to give the talk today Wednesday 29 March, and in the past when Smolin gave the talk it was usually up for download sometime the next day---Thursday.

I don't see why it should be any different. It is just Daniele coming in for a day as "substitute teacher" for Lee.

Hi Richard,
I don't know about realtime broadcast. I have been getting the Smolin lectures from the streamingmedia site anytime after they are posted. I don't know what they mean by the word "broadcast" that I see them use. To me it is just a sort of download. I hope you are having success with your computer connection getting as much (or as little) as you want.

I have learned how to skip around. I look at the "slide menu" and find a slide and then I can start it playing right at that slide and hear the spiel that goes with that slide and from thence onwards. Sometimes I'm excited and sometimes, especially if it is late at night, i almost fall asleep at the screen. Sometimes I experience frustrating bewilderment, sometimes flashes of insight.

 

[rtharbaugh1]

Hi Marcus

Yes, it seems that the rebuild at the mediasite was successful, and it is much easier to use now. I don't have to waste time downloading for hours anymore. The vid comes through right away and I can jump around forward and back as I like.

But I am never satisfied and even though I am slavishly grateful to be able to see these presentations, I still get irritable and want them to be better. I imagine editing them down to remove the hem and haw when nothing is happening. I think how wonderful it would be if I could speed them up or slow them down at will. I wish Smolin had better handwriting and that the slides would change more often, to keep up with the lecture. Sometimes I have to wait until the slide changes to see what he has written, and by then he has gone on to talk about something else.

Nevertheless the whole thing is very exciting. Many thanks for the discussion here, and Kudos for the Perimeter team that is putting this together.

Richard.

 

[marcus]

...I still get irritable and want them to be better. ...

Oh god yes. I know what you mean.

But it will take time. Smolin does not even have enough researchers to cover the interesting research problems that they've dug up. Nor do they have budget for everything that needs doing. Even though they could use more resources in the streamer department, if PI had some extra thousands $CAN I would rather see them take on another postdoc.

I'm happy the lectures are even as good as they are, and are available.

Nevertheless the whole thing is very exciting.

So glad your setup can get the lectures!

 

[Mike2]

Hi Mike2

I've been trying to get the indice idea from Baez on GR at

http://math.ucr.edu/home/baez/gr/outline2.html

but still getting stuck.

Thanks, Garret, for additional resources. I'll take a look at those.

R.

Thanks, but what I'm looking for is an introduction or perhaps even a summary of the tetrad version and how they are using the capital letter/ Greek letter indicies. I'd like to see how they are deriving the action integral using this notation and wedge product of differential forms, etc.

The references you gentle people have given so far either do not use this tetrad formalism (with the capital English letters and Greek lower case letter - It seems like they are being mixed in Rovelli's book), or these references already assume that you know all this. What do those tetrads mean again?

Rovilli references John C. Baez' $500 book, Gauge Fields, Knots, and Gravity, for an intro into the math. Does anyone know if this book introduces this tetrad formalism with the index notation that Rovelli uses and deriving these action integrals using the mathematics of diff geometry.

Thanks for trying.

 

[marcus]

Oriti's two lectures, #19 and #20, are posted, nominally ready for watching
But so far I cannot get the sound and video. All that I can get are the slides.

If anyone can get the video to actually play, please let us know.

 

[arivero]

Yep, we all found out about that price for the Baez-Munian book It's because it is out of print and very much in demand. There is supposed to be a new edition coming out, but nobody knows when. I don't know the answer to your question about the Gambini book, sorry. Maybe Baez can tell us? He does check in here every now and then.

I'd suggest to log emule/bittorrent for some scanned copy. Hmm the name of the author makes it a complex task.

 

[marcus]

I'd suggest to log emule/bittorrent for some scanned copy. Hmm the name of the author makes it a complex task.

Did you try to get Oriti's lecture #19 to play? I can't get it to work and don't know if it my computer's problem or the PI media site.

Now I see that I can't play any of the smolin lectures. I fear it must be my system acting up. Has anyone else experienced trouble with the PI streamer site recently?

 

[marcus]

I cured my computer and got Lectures #19 and 20 to play!

they asked Oriti so many questions in Lecture 20 that he did not have time to get to Group Field Theory (GFT) which was the main thing I was hoping to hear him talk about.

so at the end they set up another talk for him on Friday (which was yesterday 31 March) just for GFT.

Which AFAIK will not be available to us on streamer.

 

[marcus]

so at the end they set up another talk for him on Friday (which was yesterday 31 March) just for GFT.

Which AFAIK will not be available to us on streamer.

But in fact PI did make the extra Oriti lecture available!

It is lecture #21, given Friday 31 March
I am watching it now. It is a good lecture so far, although much interrupted by questions from the students (which one can approve of and also this time they are close enough to the mike that the questions are intelligible)

he plans to introduce GFT after discussing the example of 3D ponzano regge and also after a sketch of Feynman diagrams. the plan is:

1. 3D Ponzano-Regge

2. Feynman diagrams (just the idea)

3. Group Field Theory

 

[kakarukeys]

In Lecture 5, Lee Smolin indicated that the conjugate momenta in the Hamiltonian Formalism of Maxwell theory are densities? Anybody knows why?

\pi^\nu = - F^{0 \nu} is clearly a vector since F^{\mu\nu} is a tensor.

 

[garrett]

Yep. He's doing Maxwell theory in Minkowski spacetime -- in which \sqrt{g}=1. In a general spacetime he would have gotten a legitimate density, like \pi^\nu = \sqrt{g} F^{0 \nu}.

 

[marcus]

Lectures #22 and 23 are now online

Lectures 1-18 were given by Smolin

Lectures 19,20 and 21 were given by Daniele Oriti (the last half of #21 being especially noteworthy since an introduction to Group Field Theory)

Lectures 22 and 23 were given by Viqar Husain, who has been working on quantizing the black hole. He says that the original motivation was to "get to the bottom of hawking radiation". Hawking used a semiclassical model so it is in a sense merely heuristic. What happens if one makes a fully quantum model of the black hole? One would like to see quanta of radiation coming out. Also in Husain's work the BH singularity is shown not to exist. In the quantum model BH there is no singularity. This is what is expected to happen in QG. It is supposed to get rid of the cosmological and black hole singularities and it seems to be doing that. So far the results all involve some simplifying assumptions like spherical symmetry----now the game is to remove simplifying assumptions made earlier and show that the result works in all cases.

I haven't watched #22 and 23 yet. Will watch some today.

 

[Mike2]

Lectures #22 and 23 are now online

Lectures 1-18 were given by Smolin

Lectures 19,20 and 21 were given by Daniele Oriti (the last half of #21 being especially noteworthy since an introduction to Group Field Theory)

Lectures 22 and 23 were given by Viqar Husain, who has been working on the removal of the black hole singularity----

So how's is their presentation compared to Smolin's? Do they speak with a heavy accent? Do they write well on the board?

 

[marcus]

Smolin is not an expert in GFT (he has not yet written any GFT papers) and both Freidel and Oriti are writing GFT papers.

No course would be complete without GFT. It is the new approach which in some sense CONTAINS Loll's dynamical triangulations, and Spin Foams, and ordinary canonical LQG.
Contains in the sense that you can get models that look like these other things if you take special cases or simplify down in certain ways. Oriti explained this in Lecture #21.
he also showed a way in which you can get something that looks like Causal Sets out of GFT.
This was how he explaines why he is especially interested in the GFT approach----it seems to be at a point of convergence of various background independent QGs.

I think since a QG introduction SHOULD have GFT in it, Smolin made a good decision to invite Oriti to give some lectures about it. (and also Oriti handled Spin Foam models as well, so Smolin didn't have to cover that either)
=================

Viqar Husain is giving a special segment of the course devoted to Black Holes.

he has two lectures #22 is 1 hour 22 minutes and is all CLASSICAL.

It gradually gets more exciting as he finishes a review of earlier work and starts to present his own work that is a preparation for the quantization in the next hour.

the first place i noticed it heating up was at minute=44 on page 8 of the slide menu-----slide #3 of page 8. that is where he finishes covering Unruh's work

the next place that the energy steps up is around minute = 53, slide #7 page 9 of the slide menu.

this is where he says he will stop presenting classical----but he then remembers some interesting classical results that he will use in the quantization, so he continues for the next 25 minutes giving these classical results, which I found quite interesting.
and there were questions. So then the lecture was over.

I suppose all the quantum black hole treatment is in Lecture 23.
================
Mike asked about presentation. Both are excellent. Very crisp and organized and on top of the material.
Oriti has what i would call a clipped French accent-----both Oriti and Husain talk fast but clearly.

Oriti says "tetrahedron" faster than an American, so you may not understand it. the way he says it sounds like "tetredre" or tetr-édre. I assume this is the French word.
=================
In Lecture #23 which I just watched Viqar Husain goes over his own work (with Oliver Winkler) and he gives these references to papers---to read as supplement to the hour lecture.
http://arxiv.org/gr-qc/0410125
Quantum resolution of black hole singularities
http://arxiv.org/gr-qc/0412039
Quantum black holes from null expansion operators
http://arxiv.org/gr-qc/0503031
Flat slice Hamiltonian formalism for dynamical black holes
http://arxiv.org/gr-qc/0601082
Quantum Hamiltonian for gravitational collapse

=========================
EDIT:response to the next post.
Mike, I think not. I do not believe there is a simple relation between Group Field Theory
(a way to realize spinfoam models by integrating over powers of the group with Haar measure)
and Algebraic quantum field theory
But I will defer to others about this. they may be able to see some analogy or connection.
Personally I see none

 

[Mike2]

No course would be complete without GFT. It is the new approach which in some sense CONTAINS Loll's dynamical triangulations, and Spin Foams, and ordinary canonical LQG.
Contains in the sense that you can get models that look like these other things if you take special cases or simplify down in certain ways. Oriti explained this in Lecture #21.
he also showed a way in which you can get something that looks like Causal Sets out of GFT.
This was how he explaines why he is especially interested in the GFT approach----it seems to be at a point of convergence of various background independent QGs.

Would this be the same as Algebraic QFT that relies on the Hilbert space of operator algebras more than on the Hilbert space of eigenstates of those operators? From what I'm reading this language seems to be emerging in various efforts. It seems this operator algebra approach allow us not to depend on the background used to describe the eigenstate of a given operator... or something like that. And it seems that group theory (of GFT) is a subsection of Abstract Algebra on which Algebraic QFT is based. I plan on getting more into this subject one I get more time. But I'm working overtime these days, and I still have to do my taxes

 

[marcus]

Lectures #24 and #25 are out. Both given by Lee Smolin.

I have watched over half of #24. It is about braid preons, how they fit in with spin networks and provide a standard model worth of matter. helpful---gives intuitive ways think about this. One of the best lectures in the series.

To skip to framed links, twists, and the braid group begin at page #6 of the slide list, or at top of page #7-----spin network labels can apparently be eliminated (?)

To skip to where the topological preon model is introduced, begin at page #9.

what he is talking about now is energy and momentum given interpretation as topological invariants

=====================

just came to the end of 24, where he announces that the next hour, #25, will be about DSR.

great series, here is the link again if anyone hasnt been watching them:
http://streamer.perimeterinstitute.ca:81/mediasite/viewer/FrontEnd/Front.aspx?&shouldResize=False

go down the lefthand sidebar menu to Intro to QG

 

[marcus]

"hossi"

Smolin lecture #25 seems to be the final one in the series.

BTW there is a brief mention of Bee Hossenfelder's work in #25.

He is discussing remaining open problems in QG and some current/future research. The mention of Bee ("hossi" at PF) comes at page 8 of the slide list, the 3rd slide on that page.

In lectures #24 and #25 there is some interesting "self-criticism" where Smolin indicates what he thinks are some "points of vulnerability" of QG theories. These are some theoretical weak points and also some generic predictions that might be falsified experimentally---(or maybe one should call those strong points, since a scientific theory is supposed to be empirical and cannot be that unless it is falsifiable). However you regard it, at the end of the series of lectures Smolin takes a CRITICAL look at QG theory, Loop in particular, and points to open questions.

 

[hossi]

BTW there is a brief mention of Bee Hossenfelder's work in #25.

oops , refers to this work

http://arxiv.org/abs/hep-th/0305262"
hep-th/0305262

or, easier to read:

http://arxiv.org/abs/hep-ph/0410122"
hep-ph/0410122

Regarding the soccer ball problem (last seconds...), see also section III of

http://arxiv.org/abs/hep-th/0603032"
hep-th/0603032



B.

 

[marcus]

oops , refers to this work

http://arxiv.org/abs/hep-th/0305262"
hep-th/0305262

or, easier to read:

http://arxiv.org/abs/hep-ph/0410122"
hep-ph/0410122

Regarding the soccer ball problem (last seconds...), see also section III of

http://arxiv.org/abs/hep-th/0603032"
hep-th/0603032
B.

Is that just a blush of modesty? I think it was nice to get a mention in the last lecture of the series---not at all embarrassing, quite the opposite!

You had a question about Rovelli's paper Relational EPR and I thought Alejandro Satz might like to tackle it so I just mailed it to his blog:

http://realityconditions.blogspot.com/2006/04/relational-quantum-mechanics.html#c114506090118144509

I enjoyed your blog entry Wine and Cheese Physics with the German pop song. I like rhymed songs and it reminded me a little of some wonderful songs in the musical play Marat/Sade.

Your blog Backreaction has a link to Satz blog Reality Conditions, which in turn has a reciprocal link to Backreaction. Maybe it is the first sprouting out of the ground of a quantum gravity blog network. which might be nice.

 

[hossi]

Maybe it is the first sprouting out of the ground of a quantum gravity blog network. which might be nice.

Indeed. I am not a friend of communities, but it's become quite difficult to keep track of the status of recent research. There is just so much stuff being published, too much lectures, seminars, new books, etc. When used with appropriate caution, blogs and forums like this one can fulfil the very important purpose to keep people together and connect lines of thoughts.



B.