What is the recent development of Loop Quantum Gravity

tom.stoer

very interesting, but many difficulties in the spin foam approach (you what I am talking about ;-) are still not addressed

marcus

Of course ;-)
A basic premise of this thread is that there are plenty of well-defined problems to work on.

That is what this thread is fundamentally about: current progress in solving problems, essentially by gradually redefining the theory.

The story can be told, to some extent, in human terms. There are people who not only identify problems but also do something about them.

Alesci focused on a problem with the Thiemann hamiltonian and proposed a new hamiltonian (able to grow volume). He is now joining Lewandowski's Warsaw group as postdoc.
http://sites.google.com/site/grqcrumourmill/

Engle focused on a problem with largescale limit of the EPRL vertex and proposed a solution which prefigured the one in the "Discrete Symmetries" paper just mentioned. He is now faculty at Florida Atlantic.

Ryan ("Simplicity constraints and the Immirzi parameter in discrete quantum gravity" ILQGS) has accepted a tenure track position at Morelia.
http://relativity.phys.lsu.edu/ilqgs/ryan041211.pdf
http://sites.google.com/site/grqcrumourmill/

At each stage there is a rather well-defined theory, which gives focus to the program, and there are opportunities for young researchers to do things which are clearly significant.

marcus

Here's an indication of interests in the broader community of Mathematical Physics. Some of the speakers' names will be familiar to people at BtSM forum especially those who have been following developments in Group Field Theory/Loop-and-allied QG research.

==quote==
The XXIX International Colloquium on Group-Theoretical Methods in Physics
August 20-26, 2012, Chern Institute of Mathematics, Tianjin, China

Plenary Speakers (Titles and Abstracts)

Akito Arima (Musashi Gakuen, Japan)
Abhay Ashtekar (Pennsylvania State University, USA)
Murray Batchelor (Australian National University, Australia)
Edward Corrigan (University of York, UK)
Mo-Lin Ge (Nankai University, China)
Razvan Gurau (Perimeter Institute for Theoretical Physics, Canada) (Hermann Weyl Prize Awardee)
Alden Mead (University of Minnesota, USA) (Wigner Medal Awardee)
Jerzy Lewandowski (University of Warsaw, Poland)
Jun Murakami (Waseda University, Japan)
Daniel Treille (CERN, Switzerland) (Public Lecturer)
Vincent Rivasseau (University Paris-Sud XI, France)
Zhenghan Wang (Microsoft Station Q, USA)

The time allocated for each plenary talk is 60 minutes (50 min presentation + 10 min questions).
==endquote==
This time the biennial Group-Theory-in-Physics Conference will have 12 parallel sessions, of which #8 is "Loop Quantum Gravity", and #9 is "Group Field Theory for Quantum Gravity".
I'm hoping that the titles of the talks (plenary 60 minute and parallel 30 minute) will be posted soon and that we can get from them some idea of how particular foci of interest are shaping up.
http://www.nim.nankai.edu.cn/activit...nouncement.pdf

http://www.cim.nankai.edu.cn/activit...0820/index.htm

marcus

A week from today there will be two Loop talks at Perimeter, which we can expect to have available as online PIRSA video.
http://www.perimeterinstitute.ca/en/...xt=1338177600/

The first, at 2PM, will be the PI Colloquium talk, given by Eugenio Bianchi. Here's the Pirsa link:
http://pirsa.org/12050053
Then at 4PM there will be a QG seminar talk by Hal Haggard.
Haggard got his PhD in Loop QG from UC Berkeley last year and has been teaching courses in the Physics department at Berkeley for the past couple of semesters.
Here is the abstract and Pirsa link for his talk:

http://pirsa.org/12050084
Pentahedral Volume, Chaos, and Quantum Gravity
Speaker(s): Hal Haggard
Abstract: The space of convex polyhedra can be given a dynamical
structure. Exploiting this dynamics we have performed a Bohr-Sommerfeld
quantization of the volume of a tetrahedral grain of space, which is in
excellent agreement with loop gravity. Here we present investigations of the
volume of a 5-faced convex polyhedron. We give for the first time a
constructive method for finding these polyhedra given their face areas and
normals to the faces and find an explicit formula for the volume. This results
in new information about cylindrical consistency in loop gravity and a couple
of surprises about polyhedra. In particular, we are interested in discovering
whether the evolution generated by this volume is chaotic or integrable as this
will impact the interpretation of the spin network basis in loop gravity.
Date: 30/05/2012 - 4:00 pm

Later this summer, Haggard will be one of the invited speakers at the "Groups 29" (Group Theoretical Methods in Physics) conference mentioned in the previous post. He then takes up a 2-year postdoc fellowship at Marseille starting in September. Part of the prior work referred to in the abstract is research he co-authored with Bianchi.