Berkeley prof contributes LQG paper

Your Name]In summary, there has been an interesting development in the field of quantum gravity at UC Berkeley, where LQG research is being conducted. One of the senior authors leading this research is Robert Littlejohn, an accomplished physicist with a Ph.D. from UC Berkeley. Littlejohn is best known for his research in Plasma Physics and Nonlinear Dynamics. Recently, he and his PhD student, Hal M. Haggard, published a paper on the asymptotics of the Wigner 9j symbol, which has connections to the Ponzano-Regge formula and the Einstein-Hilbert action in 3-dimensional gravity. The paper presents rules for converting spin networks into geometrical figures and discusses the symmetries of the
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Interesting development. We already knew nonstring QG at UC Davis, but hadn't heard of LQG research in the UC Berkeley physics department.
The acknowledgments thanked Rovelli among others, for discussions and hospitality---at least one of the authors must have visited Marseille and Pavia* while doing the research.
The senior author is Robert Littlejohn, impressive guy
http://physics.berkeley.edu/index.p...gement&act=people&Itemid=299&task=view&id=478
"Robert Littlejohn received his B.A. in 1975 and his Ph.D. in 1980, both from the University of California at Berkeley. After postdoctoral positions at the La Jolla Institute and the University of California, Los Angeles, he joined the Berkeley faculty in 1983. He has been a Presidential Young Investigator and a Miller Professor, and he is a fellow of the American Physical Society."
Now full professor at Berkeley best known for research in Plasma Physics And Nonlinear Dynamics. Here is a page on his research interests:
http://www.physics.berkeley.edu/research/faculty/littlejohn.html [Broken]

MTd2 spotted the paper by Littlejohn and Haggard (PhD student working with Littlejohn):
http://arxiv.org/abs/0912.5384
Asymptotics of the Wigner 9j symbol
Hal M. Haggard, Robert G. Littlejohn
(Submitted on 29 Dec 2009)
"We present the asymptotic formula for the Wigner 9j-symbol, valid when all quantum numbers are large, in the classically allowed region. As in the Ponzano-Regge formula for the 6j-symbol, the action is expressed in terms of lengths of edges and dihedral angles of a geometrical figure, but the angles require care in definition. Rules are presented for converting spin networks into the associated geometrical figures. The amplitude is expressed as the determinant of a 2x2 matrix of Poisson brackets. The 9j-symbol possesses caustics associated with the fold and elliptic and hyperbolic umbilic catastrophes. The asymptotic formula obeys the exact symmetries of the 9j-symbol."

http://compassproject.berkeley.edu/bio.php?profile=hal [Broken]

Here is how their paper starts out:
"The asymptotic behavior of spin networks has played a significant role in simplicial approaches to quantum gravity. Indeed, the field began with the observation that the Ponzano-Regge action(1968) for the semiclassical 6j-symbol is identical to the Einstein-Hilbert action of a tetrahedron in 3-dimensional gravity in the Regge formulation (Regge, 1961;...)
...
...In this article we present the generalization of the Ponzano-Regge formula to the Wigner 9j-symbol, as well as some material relevant for the asymptotics of arbitrary spin networks..."

*Pavia, see article "Quantum Tetrahedra" http://pubs.acs.org/doi/abs/10.1021/jp909824h
 
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Thank you for bringing this interesting development to our attention. It is always exciting to see new research being conducted in the field of quantum gravity. I was not aware of the LQG research happening at UC Berkeley and I am glad to see that it is being led by such an accomplished scientist like Robert Littlejohn.

The paper by Littlejohn and Haggard on the asymptotics of the Wigner 9j symbol seems like a significant contribution to the field. The fact that it obeys the exact symmetries of the 9j-symbol is particularly intriguing and I look forward to reading more about their findings.

I also found it interesting that the paper mentions the connection between the Ponzano-Regge formula and the Einstein-Hilbert action in 3-dimensional gravity. It seems like this could have implications for our understanding of quantum gravity in higher dimensions as well.

Thank you again for sharing this information and I will definitely be keeping an eye out for future developments from Littlejohn and his team at UC Berkeley.


 
  • #3


Thank you for sharing this exciting development in the field of quantum gravity research. It is interesting to see that there is now LQG research being conducted at UC Berkeley, in addition to the work being done at UC Davis. The fact that the paper acknowledges discussions and hospitality with Rovelli and others at Marseille and Pavia suggests a collaborative effort between different institutions, which is always promising for advancing scientific knowledge.

It is also impressive to see that the senior author of the paper, Robert Littlejohn, has a strong background in plasma physics and nonlinear dynamics. The research interests listed on his page at UC Berkeley show a diverse range of topics, further highlighting his expertise in various fields of physics.

The paper itself, on the asymptotics of the Wigner 9j symbol, seems to have significant implications for the study of quantum gravity and the use of spin networks in simplicial approaches. It is encouraging to see that this field is continuing to grow and evolve, with new developments and collaborations emerging.

Overall, this is an exciting contribution to the study of nonstring quantum gravity and it will be interesting to see how it impacts future research in this area. Thank you for sharing this information.
 

What is LQG?

LQG stands for Loop Quantum Gravity, which is a theoretical framework that aims to reconcile the theories of general relativity and quantum mechanics.

Who is the Berkeley professor who contributed to the LQG paper?

The Berkeley professor who contributed to the LQG paper is Dr. Carlo Rovelli, a renowned theoretical physicist and one of the pioneers of Loop Quantum Gravity.

What is the significance of this paper?

This paper is significant because it presents new ideas and insights into the field of Loop Quantum Gravity, which is still a relatively new and developing area of research. It also adds to the body of knowledge and understanding of the fundamental laws of the universe.

What are the potential applications of LQG?

Currently, there are no specific applications of LQG, as it is still a theoretical framework and has not been experimentally proven. However, it could potentially lead to a unified theory of physics, which could have significant implications for our understanding of the universe and technology.

What are the next steps for this research?

The next steps for this research would be to continue exploring and developing the ideas presented in the paper, conducting experiments and observations to test the validity of the theories, and collaborating with other scientists to advance the field of Loop Quantum Gravity.

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