New stuff happening in Quantum Gravity

[marcus]

Simone Speziale is teaching an introductory course on LQG, and Perimeter has the videos online.
Lecture #1, 5 February:
http://pirsa.org/08020008/

Lecture #2, 7 February:
http://pirsa.org/08020012/
=====================

Lee Smolin is giving a more advanced QG course and there are about eight lectures online so far.
Lecture 1
http://pirsa.org/08010033/
Lecture 2A
http://pirsa.org/08010034/
Lecture 2B
http://pirsa.org/08010040/
Lecture 3A
http://pirsa.org/08010035/
Lecture 3B
http://pirsa.org/08010041/
Lecture 4
http://pirsa.org/08010036/
Lecture 5A
http://pirsa.org/08020024/
Lecture 5B
http://pirsa.org/08020029/
==================
Kirill Krasnov has given a talk on SELF DUAL GRAVITY at the ILQGS, for which the slides are available.
http://relativity.phys.lsu.edu/ilqgs/krasnov020508.pdf
Here is the Spring 2008 schedule for the ILQGS
http://relativity.phys.lsu.edu/ilqgs/schedulesp08.html
Jan 22 Quantum gravity and the information loss problem Madhavan Varadarajan Raman Research Institute
Feb 5 Self Dual Gravity Kirill Krasnov University of Nottingham
Feb 19 Improved effective equations in loop quantum cosmology Victor Taveras PennState
Mar 11 TBA
Mar 25 Manifestly gauge invariant relativistic perturbation theory Kristina Giesel AEI
Apr 8 TBA
Apr 22 New developements in the definition of the spinfoam vertex, and the loop-spinfoam relation Carlo Rovelli Marseille
May 6 QFT in Cosmological Space Times from LQC Speaker TBA
For more information and links here is the main ILQGS page:
http://relativity.phys.lsu.edu/ilqgs/

==================
Yidun Wan's seminar on network braid matter states
http://pirsa.org/08010044/
==================

Renate Loll's group has recently posted two papers applying CDT (causal dynamical triangulations) to non-critical string (field) theory. "Extra dimensions" are not required in this approach.

 

[marcus]

The Utrecht Triangulations QG group, that Renate Loll belongs to, has been busy in the past 6 months and has come out with several papers some of which go in unexpected directions (at least not expected by me.) Here are some papers since September 2007.
1. http://arxiv.org/abs/0802.0896
Title: Topology change in causal quantum gravity
Authors: J. Ambjorn, R. Loll, Y. Watabiki, W. Westra, S. Zohren
Comments: 4 pages, proceedings of the workshop JGRG 17 (Nagoya, Japan, December 2007)

2.http://arxiv.org/abs/0802.0719
Title: A String Field Theory based on Causal Dynamical Triangulations
Authors: J. Ambjorn, R. Loll, Y. Watabiki, W. Westra, S. Zohren
Comments: 29 pages, 4 figures

3. http://arxiv.org/abs/0712.2485
Title: Planckian Birth of the Quantum de Sitter Universe
Authors: J. Ambjorn, A. Gorlich, J. Jurkiewicz, R. Loll
Comments: 4 pages, 3 figures

4. http://arxiv.org/abs/0711.0273
Title: The Emergence of Spacetime, or, Quantum Gravity on Your Desktop
Authors: R. Loll
Comments: 21 pages, 11 figures, write-up of plenary talk at GR18, Sydney, July 2007

5. http://arxiv.org/abs/0709.2784
Title: Putting a cap on causality violations in CDT
Authors: J. Ambjorn, R. Loll, W. Westra, S. Zohren
Comments: 17 pages, 4 figures

I've highlighted a paper with Watabiki, dealing with a low-dimension case of string field theory.

On 11 February Pedro Machado, a PhD student of Loll's, will give a talk at the Utrecht ITP on
Exact RG flows, asymptotic safety and f(R) gravity
It points up the close relation between CDT and the Asymptotic Safety approach of Reuter, Percacci, Saueressig, and others.
Machado just posted a paper he did with Saueressig.
http://arxiv.org/abs/0712.0445

====================================
THIS IS NOT A NEW SOURCE but since a lot is happening recently with Triangulations QG some people might want to know the best quick introduction to this approach. Geoff C just reminded me of a 50 minute video of a November 2005 talk at Perimeter by Loll.
http://pirsa.org/05110012/
Loll has also written several review papers for nonspecialists, and some SciAm level stuff for general audience. These are listed at her website in either the Publications section or the Press section.
http://www.phys.uu.nl/~loll/Web/title/title.html
http://www.phys.uu.nl/~loll/Web/publications/publications.html

 

[Micha]

Great, Marcus. I didn't know about the Speziale stuff.

 

[marcus]

UPDATE Simone Speziale is teaching an introductory course on LQG, and Perimeter has the videos online.
Lecture #1, 5 February:
http://pirsa.org/08020008/

Lecture #2, 7 February:
http://pirsa.org/08020012/

Lecture #3, 12 February
http://pirsa.org/08020009/
=====================

Lee Smolin is giving a more advanced QG course and there are about ten lectures online so far.
Lecture 1
http://pirsa.org/08010033/
Lecture 2A
http://pirsa.org/08010034/
Lecture 2B
http://pirsa.org/08010040/
Lecture 3A
http://pirsa.org/08010035/
Lecture 3B
http://pirsa.org/08010041/
Lecture 4
http://pirsa.org/08010036/
Lecture 5A
http://pirsa.org/08020024/
Lecture 5B
http://pirsa.org/08020029/
Lecture 6A
http://pirsa.org/08020025/
Lecture 6B
http://pirsa.org/08020030/
==================
Kirill Krasnov has given a talk on SELF DUAL GRAVITY at the ILQGS, for which the AUDIO is now available.http://relativity.phys.lsu.edu/ilqgs/krasnov020508.mp3
When I posted earlier only the slides were available.
http://relativity.phys.lsu.edu/ilqgs/krasnov020508.pdf

The audio has some noise problems for the first 2/5 or 3/8 of the talk. But this part is non-essential overview and introduction. You can drag the Quicktime button over about 40 percent and it will restart on the good part. This will correspond to around slide #17, as I recall, but that is where the equations begin. Equation (1) and (2) are right around slide #17, as I recall.

It is an interesting talk. Ashtekar and Rovelli and Smolin were all asking Krasnov a lot of questions. I think the course of lectures that Smolin is now giving dovetails with Krasnov's new approach and provides background to it.

 

[marcus]

John Baez and Bertram Kostant each gave talks relating to E₈
at UC Riverside recently. Each talk was great in its own way and should get special mention. There should be a list of the best one-hour math videos, these would be on.

Here's the Baez talk
http://mainstream.ucr.edu/baez_02_12_stream.mov

Here's the Kostant talk
http://mainstream.ucr.edu/baez_02_12_guest_stream.mov
and here are Baez' notes from Kostant's talk, which can help you understand the video
http://math.ucr.edu/home/baez/kostant/summary.html

Kostant has given the talk at a number of universities. At UC San Diego, the announcement of the talk said:

Prof. Bertram Kostant Massachusetts Institute of Technology
On some of the mathematics in Garrett Lisi’s E(8) Theory of Everything
Abstract:
A physicist, Garrett Lisi, has published a highly controversal, but fascinating, paper purporting to go beyond the standard model in that it uni es all 4 forces of nature by using as gauge group the exceptional Lie group E(8). My talk, strictly mathematical, will be about an elaboration of the mathematics of E(8) which Lisi relies on to construct his theory.

Sunday, February 17, 2008 2:00 PM

Baez talk is a remarkably clear introduction to E₈ in which you learn what a a Dynkin diagram is and how to use them and think about them.
It starts with the densest way to lay out pennies on a table, and the densest way to stack oranges. In other words, a really intuitive visual down-to-earth approach to classifying Lie groups where you learn a lot more than you realize or bargained for.

And the Baez talk is the best possible entrylevel one hour preparation to watch the Kostant video. Which is mostly too technical for me to follow but can give you a whiff of an idea now and then.

It's good to have a reminder to check ILQG regularly for new online seminars:
http://relativity.phys.lsu.edu/ilqgs/

Victor Taveras recently gave a talk on Effective Equations for Loop Quantum Cosmology. The audio is not yet available but the PDF is here:
http://relativity.phys.lsu.edu/ilqgs/taveras021908.pdf

I'll update the Simone Speziale lectures listing. This is a really helpful introduction to Loop Quantum Gravity which treats
constrained systems, the meaning of diffeomorphism invariance, loops and spin networks:
Lecture #1, 5 February:
http://pirsa.org/08020008/

Lecture #2, 7 February:
http://pirsa.org/08020012/

Lecture #3, 12 February
http://pirsa.org/08020009/

Lecture #4, 14 February
http://pirsa.org/08020013/

Here are the Smolin lectures on Time in Quantum Gravity. I am guessing about the URLs of lectures 7A and 7B, which have not been posted yet as far as I know.
Lecture 1
http://pirsa.org/08010033/
Lecture 2A
http://pirsa.org/08010034/
Lecture 2B
http://pirsa.org/08010040/
Lecture 3A
http://pirsa.org/08010035/
Lecture 3B
http://pirsa.org/08010041/
Lecture 4
http://pirsa.org/08010036/
Lecture 5A
http://pirsa.org/08020024/
Lecture 5B
http://pirsa.org/08020029/
Lecture 6A
http://pirsa.org/08020025/
Lecture 6B
http://pirsa.org/08020030/
Lecture 7A
http://pirsa.org/08020026/
Lecture 7B
http://pirsa.org/08020031/

 

[marcus]

Pirsa fooled me! When the two Smolin lectures were posted, ones I expected would be 7A and 7B, they were listed as 6C and 6D.

And they had different url numbers!

Lecture 6C
http://pirsa.org/08020048
Lecture 6D
http://pirsa.org/08020049

So what I have in the previous post about Lectures 7A and B is wrong.

 

[starkind]

I havn't been able to get the Baez link to work. Something about real player not working. Is anyone else having this problem? I'll erase this to keep the thread clean.

 

[marcus]

I havn't been able to get the Baez link to work. Something about real player not working. Is anyone else having this problem? I'll erase this to keep the thread clean.

Richard, this is hardly clutter! Thanks for the alert. What Baez link doesn't work?
(I have a mac)

 

[xristy]

problem links to Baez's and Kostant's videos

Hello,

The links are not working for me either. If I go to http://math.ucr.edu/home/baez/kostant/ and try the links for streaming the videos, the Quicktime viewer starts up and then after awhile reports a "400 Bad response" error from the streaming server - I'm using Mac OS X 10.5.1 and Safari.

If I try either of the downloadable video links such as http://mediaserve.ucr.edu/baez/baez_02_12_stream.mov then after several minutes I get a timeout reporting that the file doesn't exist.

X

 

[marcus]

If I try either of the downloadable video links such as http://mediaserve.ucr.edu/baez/baez_02_12_stream.mov then after several minutes I get a timeout reporting that the file doesn't exist.

X

I watched the talk by Baez twice all the way through, earlier. After i saw your post I decided to try it again. This time I could not connect to the UC Riverside server.
Your guess is as good as mine. One possibility is the server is overloaded. Too many people trying to watch Baez lecture.

 

[starkind]

Still no luck with the Baez vids. Maybe it is because I run Windows and the software (quick time) appears to be an Apple product.

 

[marcus]

I'm sorry to hear you are still having trouble. things were acting up for me too, but now are back to normal.

BTW I just watched a PI talk by John Moffatt
http://pirsa.org/08020047/
It was quite interesting. Based on recent work with Toth he is making a number of
astonishing claims for his Modified Gravity scheme MOG.
It appears to cope with the Bullet Cluster data handily, and so not to be shot down in the general MOND debacle. He also says that once two parameters are fixed once and for all, there are no free parameters in the system----thus his MOG will make unequivocal predictions which can be tested.

In case anyone is interested, here is the abstract:

Modified Gravity and Its Consequences for Astronomy, Astrophysics and Cosmology
John Moffat - Perimeter Institute for Theoretical Physics

"The consequences of a modified gravity (MOG) are explored. I demonstrate how the solutions of the field equations obtained from the action principle of the MOG lead to a theory without any free, adjustable parameters or ad-hoc empirical formulae. The theory successfully explains solar system observations, the dispersion velocities of globular clusters, the rotation curves of galaxies, the mass profiles of X-ray clusters, the dispersion velocities of satellite galaxies, the Bullet Cluster and cosmological observations without exotic dark matter. The peculiar features of the recent data obtained for the merging cluster Abell 520 are discussed. MOG predicts agreement with data from the scale of the solar system to cosmological scales without dark matter. With no undetermined free parameters, the theory can be used to make firm predictions that may be verifiable in the foreseeable future."
19/02/2008

MUCH of the content of the talk can be found in a recent Arxiv posting, which makes good reading to go along with the video lecture.
http://arxiv.org/abs/0712.1796
Fundamental parameter-free solutions in Modified Gravity
J. W. Moffat, V. T. Toth
8 pages, 5 figures
(Submitted on 11 Dec 2007)

"Modified Gravity (MOG) has been used successfully to explain the rotation curves of galaxies, the motion of galaxy clusters, the Bullet Cluster, and cosmological observations without the use of dark matter or Einstein's cosmological constant. We now have the ability to demonstrate how these solutions can be obtained directly from the action principle, without resorting to ad-hoc parameter choices or empirical formulae. We obtain approximate solutions to the theory's field equations that, after the values of integration constants are determined from observation, show excellent agreement with data from the scale of the solar system to cosmological scales. With no undetermined free parameters, the theory can be used to make firm predictions that may be practically verifiable in the foreseeable future."

 

[ccdantas]

Hi all:

I cannot download Baez's video (baez_02_12_stream.mov) as well. I'm using a mac, safari, quicktime.Christine

 

[starkind]

I got the Baez vid to work on my machine by downloading a new copy of quick time from the Apple website. However, it played for a while and then broke up...after several tries, I got about 3/4 through.

Baez is teaching here at about my level of understanding. I wonder what course this is?

 

[turbo]

Hi all:

I cannot download Baez's video (baez_02_12_stream.mov) as well. I'm using a mac, safari, quicktime.


Christine

Try again, Christine. I just watched it, and though there is a nagging low-frequency hum in the audio, it was watchable.

 

[ccdantas]

Try again, Christine. I just watched it, and though there is a nagging low-frequency hum in the audio, it was watchable.

Hi turbo-1

Just tried again, but all I get is a timeout.

I have also sent a trackback to their blog from my post, but it did not appear there...

Christine

 

[turbo]

I'm using a plain-vanilla PC running XP SP2 over a DSL connection and the video came up fine. Try purging your browser's cache and see if you can connect after that.

 

[starkind]

I got through the whole Baez vid up until the last minute or so. I'd like to discuss some things about it. I am not sure about the method used to raise the dimension by adding "same sized" spheres to the spaces between spheres. I guess it works because the added spheres are removed in another dimension where the size is arbitrary. This is like when looking at a two dimensional print photograph of a three dimensional set of objects, we know that an object further away (in the third dimension) will look smaller. The new spheres look smaller, but that is because they are "farther away" in the 4th dimension.

About the idea that they are all one unit from the origin, that seems to be part of the conditions of the definition...closest kissing spheres will always be one unit from the origin, because the origin is defined as the center of the sphere, radius = 1.

I think we are finally getting down to the bones of the dimensional questions which keep coming back. People want to know how we do geometry in higher dimensions. Well, now I see how it is done. I still have to validate the method in my own mind, because I do not intuitively see the logic of merely adding new (smaller) spheres to the spaces.

I usually try to do dimensions by moving the minimal shape of a dimension in a new orthagonal direction. A point becomes a line in this way, a line becomes a plane, a plane becomes a volume. The minimum stack of spheres that requires three dimensions is the tetrahedral form, where the centers of each sphere in the group are the vertices of a tetrahedron. I try to imagine shifting that along a new orthagonal basis line, one which is at right angles to the other three. I usually choose time as the 4th basis line, and lay it down parallel to one of the 3 dimensional volumetric basis lines, so the shift is represented by a simple doubling. That part seems more or less to match the method Baez describes.

Perhaps a better way to choose a fourth basis line would be to use scale as the new basis. Then we can imagine the shift being one of size. The cubeoctahedron (3 dimensional) is expanded until a new orange fits in the spaces between. The new orange is still the same size as the originals, but the original 'old' oranges have gotten large enough to admit the 'new' oranges.

 

[marcus]

Glad you got the Baez video to run! It is a wonderful talk. I think it may echo some TWFs from back around #63-65. I haven't checked. But if so, the online TWFs could serve as lecture notes for better understanding.

Keeping up with the New Stuff theme. The program of the APS meeting in St Louis is out.
http://meetings.aps.org/Meeting/APR08/Content/1034
The meeting will be 10-15 April.
Abhay Ashtekar is giving an invited talk, as is Jorge Pullin.
http://meetings.aps.org/Meeting/APR08/APS_Invited

Ashtekar, Abhay Session B7.00002 Singularity Resolution in Loop Quantum Gravity
http://meetings.aps.org/Meeting/APR08/Event/82745
Pullin, Jorge Session M7.00002 Recent developments in loop quantum gravity
http://meetings.aps.org/Meeting/APR08/Event/83488

They expect about 1200 physicists to attend the April 2008 APS meeting. For an overview see
http://meetings.aps.org/Meeting/APR08/APS_epitome
The sessions are in alphabetical order----B is on the second day, Saturday morning 12 April.
M is halfway through the conference, Sunday afternoon 13 April.
W is at the end, Tuesday morning 15 April.

 

[ccdantas]

Wow. Right after finally seeing the first images of John Baez, my browser (Safari 2.0.4) disapeared and the program was shutdown.

Then tried Firefox 2.0.0.6. The same happened! I'm using Quicktime 7.2.

Maybe I need to upgrade, or perhaps it is because I'm running a simulation in my mac at the same time. I'll try again later.

 

[starkind]

This morning the internet is incredibly slow...took an hour to get here. I wonder if this is www- wide. Heard something on TV last nite about a censorship program in Pakistan that got out into the web...

 

[marcus]

Christine, Richard,
so far I haven't been experiencing these troubles----except once for a while with Baez website which could have simply been overload on the server.
They sound enormously aggravating. I think they would make me consider taking up golf or knitting----anything but the internet.

I appreciate your keeping us posted for two reasons. One is that people like Turbo may be able to come up with useful suggestions. they may understand what is going on and help. the other is that for (uncomprehending people like) me it serves as a warning of how quickly web ailments can develop and seize both clueless and clueful alike

 

[starkind]

Hi Marcus

I took up a long walk and stopped into an internet cafe along the way. Things are working there, so it was my system again. Shut it down and started all over and it is working now.

The main weirdness in my system is that the sound cuts out often. Even the speaker volume icon on the task bar dissappears. I fiddle around in the menus until it comes back on again, but I never can seem to figure out what I did, if anything, that made the difference.

I'll try the Kostant video again now.

 

[xristy]

still problems with accessing Baez and Kostant

It is excellent that others are having success. I am located in Nepal and have comparatively low bandwidth options available. Normally I prefer to download audio and video lectures rather than stream as bandwidth is insufficient for streaming.

I have no problems downloading from Perimeter Institute or other locations so it's not a generic problem with Nepal or my system - Mac OS X 10.5.1.

Now when I try the "downloadable video" links on the page at http://math.ucr.edu/home/baez/kostant/ I get a prompt asking for a username and password - this is a change from the previous timeout waiting for a connection that was occurring.

When I try to access the "streaming video" links - which are on "mainstream.ucr.edu" rather than "mediaserve.ucr.edu" I get "Bad Request" from Quicktime, VLC and Firefox. Trying the same on Windows XP, I get the same results. I have tried with two different Internet Service Providers and get the same response so it would not seem to be a specific operating system or service provider. Is it the fact that I am accessing from Nepal (which is easy to discover via the IP addresses)?

In any event I did send an email to Baez but got no reply - which I didn't really expect.

ciao,
X

 

[pelastration]

I think we are finally getting down to the bones of the dimensional questions which keep coming back. People want to know how we do geometry in higher dimensions. Well, now I see how it is done. I still have to validate the method in my own mind, because I do not intuitively see the logic of merely adding new (smaller) spheres to the spaces.

Riemann originally used a crumpled paper sheet (becoming a multilayered ball) to explain hidden and added dimensions. You can interpret this as folded subsets (local origami), not just spheres. A 2D-membrane can create that way - locally - 3D-subsets. The 3D-subsets are however still 2D-membrane.

Dirk

 

[ccdantas]

It is excellent that others are having success. I am located in Nepal and have comparatively low bandwidth options available. Normally I prefer to download audio and video lectures rather than stream as bandwidth is insufficient for streaming.

I have no problems downloading from Perimeter Institute or other locations so it's not a generic problem with Nepal or my system - Mac OS X 10.5.1.

Now when I try the "downloadable video" links on the page at http://math.ucr.edu/home/baez/kostant/ I get a prompt asking for a username and password - this is a change from the previous timeout waiting for a connection that was occurring.

When I try to access the "streaming video" links - which are on "mainstream.ucr.edu" rather than "mediaserve.ucr.edu" I get "Bad Request" from Quicktime, VLC and Firefox. Trying the same on Windows XP, I get the same results. I have tried with two different Internet Service Providers and get the same response so it would not seem to be a specific operating system or service provider. Is it the fact that I am accessing from Nepal (which is easy to discover via the IP addresses)?

In any event I did send an email to Baez but got no reply - which I didn't really expect.

ciao,
X

Hello. What ou describe appears to be exactly my situation. I'm trying to access from Brazil with no success. I have no problem downloading PI/PIRSA videos.

Good luck anyway.

Christine

 

[ccdantas]

I've just reported this problem directly at his blog (n-Category Café). Let us see if the problem can be identified and solved.

Christine

 

[marcus]

This year's main QG conference will be at Nottingham UK in early July.
The conference now has a website:
http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

They call it the "QG²" conference---QG squared for Quantum Geometry and Quantum Gravity.
So for typographical ease it gets written "QG2"

The website has the list of organizers, a preliminary program statement, the advisory panel, and roughly fifty participants who have registered so far (I didn't count, just eyeballed).

 

[marcus]

There are links to four more of the Smolin lectures on Time in Quantum Gravity.
Lecture 1
http://pirsa.org/08010033/
Lecture 2A
http://pirsa.org/08010034/
Lecture 2B
http://pirsa.org/08010040/
Lecture 3A
http://pirsa.org/08010035/
Lecture 3B
http://pirsa.org/08010041/
Lecture 4
http://pirsa.org/08010036/
Lecture 5A
http://pirsa.org/08020024/
Lecture 5B
http://pirsa.org/08020029/
Lecture 6A
http://pirsa.org/08020025/
Lecture 6B
http://pirsa.org/08020030/
Lecture 6C
http://pirsa.org/08020048
Lecture 6D
http://pirsa.org/08020049
Lecture 7A
http://pirsa.org/08020027/
Lecture 7B
http://pirsa.org/08020032/
Lecture 8A
http://pirsa.org/08030019/
Lecture 8B
http://pirsa.org/08030023/

For completeness here are the February 2008 Introduction to LQG lectures by Simone Speziale
covering constrained systems, diffeomorphism invariance, loops and spin networks:
Lecture #1
http://pirsa.org/08020008/
Lecture #2
http://pirsa.org/08020012/
Lecture #3
http://pirsa.org/08020009/
Lecture #4
http://pirsa.org/08020013/

In case anyone missed it, here's the Baez talk
http://mainstream.ucr.edu/baez_02_12_stream.mov
and the Kostant talk that went with it
http://mainstream.ucr.edu/baez_02_12_guest_stream.mov
Here are Baez' notes from Kostant's talk, which help understand the video
http://math.ucr.edu/home/baez/kostant/summary.html

 

[ccdantas]

Sorry, I forgot to post the situation back here (I answered only at n-Cat café). Now Baez's video can be downloaded without problems, but streaming still makes my browser crash.

 

[marcus]

The latest in Lee Smolin's series of lectures
Lecture 9A
http://pirsa.org/08030020/
Lecture 9B
http://pirsa.org/08030024/

The slides are available from some of the talks at the March 2008 Zakopane Loop+Foam Workshop.
Richard Kostecki, who took care of organizing the workshop, has posted the slides and earlier recommended first looking at those of Ashtekar, Thiemann, and Dittrich
http://www.fuw.edu.pl/~kostecki/zakopane08/

 

[marcus]

This year's main QG conference will be at Nottingham UK in early July.
The conference now has a website:
http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

They call it the "QG²" conference---QG squared for Quantum Geometry and Quantum Gravity.
So for typographical ease it gets written "QG2"

The website has the list of organizers, a preliminary program statement, the advisory panel, and roughly fifty participants who have registered so far (I didn't count, just eyeballed).

They now have 10 invited speakers lined up, roughly half Loop and half Noncommutative Geometry. On the Loop side it is a mix between LQG+Spinfoam and LQC (loop quantum cosmology).
About 60 registered participants so far.

Smolin's Lecture 10 video is now available online
http://pirsa.org/08030021/

 

[marcus]

The July QG2 conference now has 11 invited speakers lined up, roughly half (Loop) Quantum Gravity and half Noncommutative Geometry.
Shaping up well. 80-plus participants registered so far.

Smolin's Lecture 10 video
http://pirsa.org/08030021/

Lectures 11A and 11B
http://pirsa.org/08030022/
http://pirsa.org/08030026/

Smolin's lectures 12A and 12 B
http://pirsa.org/08040011/
http://pirsa.org/08040013/

 

[geoffc]

Audio and lectures from First Quantum Geometry and Quantum Gravity School:

http://www.fuw.edu.pl/~kostecki/school.html

 

[marcus]

The main Quantum Gravity and Quantum Geometry conference this year will be at Nottingham UK in early July.
Here is website:
http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

There are 12 invited speakers listed so far:


Abhay Ashtekar Quantum cosmology


Ali Chamseddine Connections between noncommutative geometry, spectral action and quantum gravity


Laurent Freidel The construction and semi-classical limit of spin foam models for 4d gravity


Bernard Kay The puzzles of decoherence and thermodynamical behaviour


Jerzy Lewandowski QFT in quantum curved space-time


Shahn Majid TBA


Martin Reuter Asymptotic Safety: general ideas and recent results


Vincent Rivasseau Non-commutative renormalisation


Carlo Rovelli On the relation between loops and foams


Subir Sarkar Astroparticle probes of quantum gravity


Peter Schupp Noncommutative gravity, twists and fuzzy black holes


Harold Steinacker Dynamical quantum spaces, matrix models and gravity

 

[ensabah6]

The main Quantum Gravity and Quantum Geometry conference this year will be at Nottingham UK in early July.
Here is website:
http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

There are 12 invited speakers listed so far:


Ali Chamseddine Connections between noncommutative geometry, spectral action and quantum gravity
]

marcus, Ali Chamseddine has co-authored many NCG papers with the man himself, Connes. AFAIK Ali Chamseddine hasn't published any QG papers, what type of QG does he with to show a connection to, as string theory is considered a QG and Witten-Seidberg has published papers connected ST with NCG, LQG, or something else?

 

[marcus]

It will be interesting to see how Ali Chamseddine draws the connection between QG and NCG---I expect it will be one of the more interesting talks at the conference. They now have around 120 registered participants and the list of speakers has grown since my last update on this.

http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

the conference is slightly over two months away and shaping up nicely.
At the conference site, the dual topic (QG and QG) is summarized this way:
*
Quantum gravity, including loop quantum gravity, spin foam models, 1+1 and 2+1 quantum gravity, perturbative and discrete approaches. Quantum cosmology.


*
Quantum geometry, including physical aspects of non-commutative geometry, quantum groups and quantum topology. Non-commutative field theory and deformed special relativity.

 

[ensabah6]

It will be interesting to see how Ali Chamseddine draws the connection between QG and NCG---I expect it will be one of the more interesting talks at the conference. They now have around 120 registered participants and the list of speakers has grown since my last update on this.

http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

the conference is slightly over two months away and shaping up nicely.
At the conference site, the dual topic (QG and QG) is summarized this way:
*
Quantum gravity, including loop quantum gravity, spin foam models, 1+1 and 2+1 quantum gravity, perturbative and discrete approaches. Quantum cosmology.


*
Quantum geometry, including physical aspects of non-commutative geometry, quantum groups and quantum topology. Non-commutative field theory and deformed special relativity.

I am wondering if there is a merger between the two, NCG and LQG.

Any invitations for Levin/Wen? He said he has some interest in showing up.

 

[marcus]

I am wondering if there is a merger between the two, NCG and LQG.

That is one of the things that you can see happening in the spotlight provided by these conferences. A lot of people have started thinking about this and talking about it. Jesper Grimstrup has actually co-authored several papers merging NCG and LQG. You can find them on arxiv. It is not clear if anyone has proposed the RIGHT way. Ashtekar has talked about it in a recent paper of his, in the conclusion section, as a possibility. And it is obviously what John Barrett has in mind and what the QG+QG conference is all about--the not-so-hidden agenda.

BTW the QG+QG conference is turning out to be the biggest QG conference ever. Well over 160 registered and must be approaching 200 by the looks of it now
http://www.maths.nottingham.ac.uk/r..._and_quantum_gravity_conference/participants/

I see that Renate Loll has confirmed that she will be giving a talk. It could be a condensed version of the minicourse she will be teaching at the Oporto Meeting later that month.

 

[marcus]

The confirmed speakers list for the QG+QG conference is currently as follows
(many more have registered but have not yet indicated that they will present a talk)

Aldaya Victor Instituto de Astrofisica de Andalucia-CSIC
Ashtekar Abhay Penn State
Aschieri Paulo Centro Fermi, Roma and U. Alessandria
Baratin Aristide Max Plank Institute
Barbero Fernando IEM-CSIC
Barnich Glenn University Libre de Bruxelles
Bianchi Eugenio CPT Marseille
Bonder Yuri UNAM Mexico
Borowiec Andrzej Wroclaw University & JINR, Dubna
Chamseddine Ali American University of Beirut & IHES
Fleischhack Chrstian Hamburg University
Freidel Laurent Perimeter
Giesel Kristina Albert Einstein Institute
Girelli Florian SISSA
Grosse Harald University of Vienna
Gurau Razvan Gheorghe LPT Orsay
Hinterleitner Franz Masaryk University, Czech Republic
Kay Bernard University of York
Klauder John University of Florida
Krajewski Thomas CPT Marseille
Lauda Aaron Columbia University
Lewandowski Jerzy University of Warsaw
Loll Renate University of Utrecht
Majid Shahn QMUL
Maloney Alexander McGill University
Martin-Benito Mercedes Instituto de Estrucura de la Materia-CSIC
Mikovic Aleksandar Lusofona University
Nelson William King's College, London
Noui Karim University of Tours
Oriti Daniele Institute for Theoretical Physics, Utrecht University
Pawlowski Tomasz IEM-CSIC
Perez Alejandro CPT Marseille
Picken Roger Instituto Superior Tecnico, Lisbon
Reuter Martin University of Mainz
Rivasseau Vincent University of Paris-Sud
Rovelli Carlo CPT Marseille
Ruiz Ruiz Fernando Universidad Complutense Madrid
Salminen Tapio University of Helsinki
Samanta Saurav S. N. Bose National Centre for Basic Sciences
Sarkar Subir Oxford
Schupp Peter Jacobs University Bremen
Schroers Bernd Heriot-Watt University
Skakala Jozef Victoria University of Wellington
Starodubtsev Artem CPT Marseille
Steinacker Harold Ludwig-Maximilians-University, Munich
Stephan Christoph Alexander University of Potsdam
Taveras Victor Penn State University
Tlas Tamer DAMTP, University of Cambridge
Vicary Jamie Imperial College London
Vignes-Tourneret Fabien University of Vienna

Quite a few of these are people whose work we have noted and sometimes discussed over the years since 2004 here at PF.
Those who have will in many cases find it not difficult to get an idea of the physics topics which will be discussed at conference, and some of the recent research to be presented.

 

[marcus]

Often people ask how is it proposed to merge LQG with Noncommutative Geometry. This is is specially interesting because NCG has achieved the Standard Model particle menu, and actually made some predictions of masses (measurable at LHC).

Jesper Grimstrup and co-workers has been working on this merger for some 3 years and has produced some three papers about it. One came out this year.

Presumably he will be talking about it at the July QG+QG conference. He is going to be there.
But there is something earlier. Just next week I think.
There will be a 29 May seminar talk at Perimeter.

http://pirsa.org/08050004
On Spectral Triples in Quantum Gravity
Speaker(s): Jesper Grimstrup - Neils Bohr Institute
Abstract: This talk is concerned with the existence of spectral triples in quantum gravity. I will review the construction of a spectral triple over a functional space of connections. Here, the *-algebra is generated by holonomy loops and the Dirac type operator has the form of a global functional derivation operator. The spectral triple encodes the Poisson structure of General Relativity when formulated in terms of Ashtekars variables. Finally I will argue that the Hamiltonian of General Relativity may emerge from the construction via the requirement that inner automorphisms vanish on the vacuum sector.
Date: 29/05/2008 - 4:00 am

Since it has a PIRSA number (Perimeter Institute Recorded Seminar Archive) I am expecting that the seminar will be recorded and made available like the other PIRSA seminars.
==================================

Pedro Machado got his PhD at Utrecht in Renate Loll group. He is now at Perimeter as a postdoc.
Loll's former PhD students are an interesting bunch so I also note that Machado will be giving a talk, in just a day or so actually
http://pirsa.org/08050042
Functional Renormalization Group Equations and f(R) Gravity
Speaker(s): Pedro Machado - Institute for Theoretical Physics
Abstract: After motivating and briefly reviewing the Functional Renormalization Group approach to gravity, we'll construct an FRG equation for gravitational f(R) theories. This allows us to extend the space of truncated effective average actions so far considered, giving us a better understanding of gravity FRG physics in the infrared and of the effect of non-local operators in our theories. To illustrate, we'll analyze the RG flow properties of the so-called ln(R) truncation, particularly in light of the asymptotic safety scenario.
Date: 22/05/2008 - 2:00 pm

This is in the general area of asymptotic safety that Martin Reuter works in, and Roberto Percacci, and Frank Saueressig.
Machado just did a paper with Saueressig while both were at Utrecht, and now Percacci is there. Utrecht obviously has quite a bit going in asymptotic safety as well as other approaches.
So if they record this talk too and put it online we will get a window on that as well.

Here is Saueressig and Machado's paper, to appear in Physical Review D

http://arxiv.org/abs/0712.0445
On the renormalization group flow of f(R)-gravity
Pedro F. Machado, Frank Saueressig
55 pages, 7 figures
(Submitted on 4 Dec 2007)

"We use the functional renormalization group equation for quantum gravity to construct a non-perturbative flow equation for modified gravity theories of the form S = \int d^dx \sqrt{g} f(R). Based on this equation we show that certain gravitational interactions monomials can be consistently decoupled from the renormalization group (RG) flow and reproduce recent results on the asymptotic safety conjecture. The non-perturbative RG flow of non-local extensions of the Einstein-Hilbert truncation including \int d^dx \sqrt{g} \ln(R) and \int d^dx \sqrt{g} R^{-n} interactions is investigated in detail. The inclusion of such interactions resolves the infrared singularities plaguing the RG trajectories with positive cosmological constant in previous truncations. In particular, in some R^{-n}-truncations all physical trajectories emanate from a Non-Gaussian (UV) fixed point and are well-defined on all RG scales. The RG flow of the \ln(R)-truncation contains an infrared attractor which drives a positive cosmological constant to zero dynamically"

 

[marcus]

Links to check periodically as the summer meetings gain definition
30 June Nottingham
http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/
10 July Oporto
http://faraday.fc.up.pt/omgtp2008/
18 August Cern
http://ph-dep-th.web.cern.ch/ph-dep-th/content2/workshops/strings2008/?site=content/talks.html
25 August Mit
http://www.rle.mit.edu/emergent/participants.htm

 

[marcus]

The question has been asked several times recently how are people going about merging LQG with NCG (noncommutative geometry, where Connes and Barrett have found a way to represent the standard model particles).

One approach is presented in this video talk by Jesper Grimstrup of the Bohr Institute Copenhagen
http://pirsa.org/08050004

We have four papers by Grimstrup et al that they have posted over several years, since 2005.
This talk may be helpful in understanding, because it has a bunch of Perimeter people asking questions.

Grimstrup will also be one of the participants at the Nottingham QG+QG conference that starts in one month from now (30 June). One of the main focus points of this conference is connecting Quantum Gravity with NCG. There may be several ways to do it and the approach of Grimstrup et al is one that has been worked on among the longest.
(It currently of considerable interest because it offers a way of including matter in theories like LQG.)

 

[marcus]

The QG2 conference starts 30 June. The speakers list has been updated. Here's the new list
==================

Aldaya Victor Instituto de Astrofisica de Andalucia-CSIC
Alexandrov Sergey Montpellier University
Ashtekar Abhay Penn State
Aschieri Paulo Centro Fermi, Roma and U. Alessandria
Baratin Aristide Max Plank Institute
Barbero Fernando IEM-CSIC
Barnich Glenn University Libre de Bruxelles
Bianchi Eugenio CPT Marseille
Bonder Yuri UNAM Mexico
Borowiec Andrzej Wroclaw University & JINR, Dubna
Chamseddine Ali American University of Beirut & IHES
Fleischhack Chrstian Hamburg University
Freidel Laurent Perimeter
Giesel Kristina Albert Einstein Institute
Girelli Florian SISSA
Grosse Harald University of Vienna
Gurau Razvan Gheorghe LPT Orsay
Hinterleitner Franz Masaryk University, Czech Republic
Kay Bernard University of York
Krajewski Thomas CPT Marseille
Lauda Aaron Columbia University
Lewandowski Jerzy University of Warsaw
Liberati Stefano SISSA
Loll Renate University of Utrecht
Majid Shahn QMUL
Maloney Alexander McGill University
Marciano Antonino CPT-CNRS
Martin-Benito Mercedes Instituto de Estrucura de la Materia-CSIC
Mikovic Aleksandar Lusofona University
Nelson William King's College, London
Noui Karim University of Tours
Oriti Daniele Institute for Theoretical Physics, Utrecht University
Pawlowski Tomasz IEM-CSIC
Picken Roger Instituto Superior Tecnico, Lisbon
Reuter Martin University of Mainz
Rivasseau Vincent University of Paris-Sud
Rovelli Carlo CPT Marseille
Ruiz Ruiz Fernando Universidad Complutense Madrid
Salminen Tapio University of Helsinki
Samanta Saurav S. N. Bose National Centre for Basic Sciences
Sarkar Subir Oxford
Schupp Peter Jacobs University Bremen
Schroers Bernd Heriot-Watt University
Singh Parampreet Perimeter Institute
Skakala Jozef Victoria University of Wellington
Starodubtsev Artem CPT Marseille
Steinacker Harold Ludwig-Maximilians-University, Munich
Stephan Christoph Alexander University of Potsdam
Taveras Victor Penn State University
Tlas Tamer DAMTP, University of Cambridge
Vicary Jamie Imperial College London
Vignes-Tourneret Fabien University of Vienna
==================
At this point there are 52 confirmed speakers.
There are some folks one would normally expect to present who haven't signed up to give a talk yet. This is a partial list in no particular order: a few names I remembered not seeing.
Martin Bojowald
Derek Vandersloot
Andy Randono
Derek Wise
Yidun Wan
Jesper Grimstrup
Dario Benedetti
Jeffrey Morton
Ruth Williams
Lee Smolin
This could in some cases be because their co-authors are presenting the work.
Going back over, I now see many more people whose work I have been following with interest, who are registered as participants, but not yet confirmed as giving a talk. Counting the above, maybe 20 in all. So I am wondering if there is a problem. Will there be parallel sessions to accommodate more talks, or is the number of talks limited to 50-some and there just isn't room in the conference for more? 30 June is just a month away.

 

[marcus]

The speaker list has been updated again. There are now 73 confirmed talks.
I listed some in the last post that I expected to be added, and several of these are now confirmed.
John Baez former PhD student Derek Wise is one.
Andy Görlich, one of Loll's collaborators will presumably be presenting the results on the emergence of a smooth deSitter background, from foam. He was involved in the detailed data analysis of quantum fluctuations, in the Monte Carlo simulations.
Bojowald is confirmed on board.

You can check the list out. I think it is going to be exciting, a lot of the speakers I know to have remarkable new results to report.

JESPER GRIMSTRUP IS TALKING! He is the guy at the Niels Bohr Institute Copenhagen who has been working since 2005 on welding Loop Quantum Gravity to Alain Connes Noncommutative Geometry----he and collaborators. We have discussed his work and given links to some four of his papers. This will be the first conference where Grimstrup Aastrup results are presented, if I remember right. He gave a seminar at Perimeter recently which is video online at PIRSA.

Jeffrey Morton, another John Baez PhD, has been added to the list. Aaron Lauda is already on---n-category application to QG probably.
It is shaping out that a lot of different sectors of nonstring QG (and QG) are being brought together. It is important for people to meet in conference partly because it helps them talk the same language. It helps them to converge on meaning the same things by the terms they use in communicating.

so here we are getting spinfoam, triangulations, noncommutative geometry, n-category stuff, quantum groups, LQG, Loop Quantum Cosmology, group-field-theory, asymptotic safety, and more, into the same conference

 

[marcus]

Many of the abstracts of talks scheduled for the Nottingham QG2 conference are now available:
http://www.maths.nottingham.ac.uk/r...ravity_conference/participants/abstracts.html

 

[marcus]

Many of the abstracts of talks scheduled for the Nottingham QG2 conference are now available:
http://www.maths.nottingham.ac.uk/r...ravity_conference/participants/abstracts.html

Today when I counted, 62 abstracts were posted so you can get a good overview of what the talks will cover. I was especially interested by the abstracts for two of the talks, Eugenio Bianchi's and that of Florian Conrady (on joint work with Laurent Freidel). Looks like a lot of progress towards confirming the classical limit of loop/spinfoam and also towards bringing together with triangulations (cdt) path integral approach. Probably this is a big year in quantum geometry/gravity.

Lee Smolin will be giving a talk. He has not posted an abstract so we don't know the topic.

There are a total of 75 talks confirmed-----the 62 where we have the abstracts already and the others where we mostly only have the titles.
http://www.maths.nottingham.ac.uk/r...y_and_quantum_gravity_conference/participants

 

[marcus]

There are now 66 abstracts posted.

In what appears to be a last minute change, Yidun Wan will be giving a talk on 4-valent braid-matter. It sounds like a pretty interesting talk, judging from the abstract.
==quote==
Yidun Wan
C, P, T, and Conserved Quantities of Braid Excitations in Quantum Gravity

We derive conservation laws from interactions of braid-like excitations of embedded framed spin networks in Quantum Gravity. We also demonstrate that the set of stable braid-like excitations form a noncommutative algebra under braid interaction, in which the set of actively-interacting braids is a subalgebra. We show that four-valent braids allow seven and only seven discrete transformations. These transformations can be uniquely mapped to C, P, T, and their products. Each CPT multiplet of actively-interacting braids is found to be uniquely characterized by a non-negative integer. Finally, braid interactions turn out to be invariant under C, P, and T.
==endquote==

Looks like Smolin can now sit back and let others of the Perimeter group present the new braid-matter developments----Jon Hackett and Yidun Wan, possibly others as well.

To me it looks suspiciously like the first stage of the braid-matter program has succeeded.

It's going to be a lively conference: counting some dozen or so plenary speakers not included in the abstracts list, the total comes to around 78 talks. Several of the talks are apt to present landmark results. (I mentioned Eugenio Bianchi and Florian Conrady earlier. It's worthwhile to have a look at the abstracts of their talks, among others.)

 

[marcus]

Here is what the program for the week looks like
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/QGsquared-timetable

Lee Smolin will be chairing a discussion at the end----Friday 11:30AM to 1:00PM---
apt to be a "Where do we go from here?" summary and prospects discussion.

Most days lunch starts at 12:30PM. On each of the five days, M-F, there will be 3 one-hour morning slots for plenary speakers-----the 14 plenary talks we know about plus the overview concluding discussion chaired by Smolin.

In addition there are 60 some parallel session talks, which are scheduled for the afternoons of three days
Monday:
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/Monday_Parallel_Sessions
Tuesday:
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/Tuesday_Parallel_Sessions
Thursday:
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/Thursday_Parallel_Sessions

These talks are alotted 30 minutes each. There are three lecture halls, each session runs 4 hours, from 2PM to 6PM-----allowing either for 8 talks or else 7 talks plus a halfhour discussion period at the end.

 

[marcus]

Here is what the program for the week looks like
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/QGsquared-timetable

...

On each of the five days, M-F, there will be 3 one-hour morning slots for plenary speakers-----the 14 plenary talks we know about plus the ... concluding discussion...

In addition there are 60 some parallel session talks, which are scheduled for the afternoons of three days
Monday:
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/Monday_Parallel_Sessions
Tuesday:
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/Tuesday_Parallel_Sessions
Thursday:
http://echo.maths.nottingham.ac.uk/qg/wiki/index.php/Thursday_Parallel_Sessions

These talks are alotted 30 minutes each. There are three lecture halls, each session runs 4 hours, from 2PM to 6PM-----allowing either for 8 talks or else 7 talks plus a halfhour discussion period at the end.

since I posted that, there has been a change. the discussion at the end of the conference will be chaired by Vincent Rivasseau
the QG2 conference website says that all the scheduling is complete, in final form to be printed out for inclusion in the information packets.
It looks to be a major success. Good luck to the organizers and participants!
===========================

Earlier I mentioned that Rovelli will be giving a talk on LQG at the annual strings conference "Strings 2008" to be held this year at CERN in August. I gave a link in Announcements to the list of summary and research talks.
http://ph-dep-th.web.cern.ch/ph-dep-th/content2/workshops/strings2008/?site=content/talks.html
and there was some discussion here
https://www.physicsforums.com/showthread.php?t=235532
At that time only the speakers names were listed. Now many of the titles of the talks have been filled in.

There are 9 "survey" talks and 30 briefer "research" talks. Rovelli's is one of the latter.

It is remarkable that 4/9 of the lengthier "survey" talks are not about string.

Also that little or nothing is being said about the String Landscape and the speculation about "multiverses". No survey talk. Little or nothing of that sort evident yet in the research talk listing either AFAICS. What was fashionable and receiving much attention 2 or 3 years ago is no longer in evidence.

Also no talk by Susskind, or by Witten---neither have registered to attend so far. Gary Horowitz has not registered. Steve Giddings has registered but is not giving a talk. There is an odd sense that the face of the field has changed.

All the talks will be plenary session. Just one auditorium. No sessions running in parallel in different halls. The CERN hosts are running a nice tight format. And I can't overemphasize what a positive development I think it is for them to have included a talk about the Loop Quantum Gravity/Spinfoam approach by Carlo Rovelli.

somebody obviously thinks it is important for the two research communities to talk to each other.