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Loops '05

  1. Oct 6, 2005 #1

    john baez

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    A friend of mine offered to videotape talks at Loops '05, so I contacted Thomas Thiemann (one of the organizers) - and he said that they're already planning to videotape the conference!

    So, eventually you'll be able to see all the talks.

    But there's no need to wait if you want to see mine. :tongue2:
     
  2. jcsd
  3. Oct 6, 2005 #2

    marcus

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    JB's lecture notes are interesting and provocative. Hope others read them and we can discuss some of the meaty/gristly parts at this thread.
     
    Last edited: Oct 7, 2005
  4. Oct 7, 2005 #3

    Chronos

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    Thanks, JB!
     
  5. Oct 10, 2005 #4

    garrett

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    Since I live in Maui, there aren't many times I wish I were somewhere else in the world -- but this week is one of them. Someone please post when these videos and other materials are up on the net. Thanks!
     
  6. Oct 10, 2005 #5

    marcus

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    I feel the same way about the Berkeley hills looking out over the bay-----that is, I wish I were in the Berlin area right now and it is an unfamiliar sensation.

    I remember checking your garrett lisi website out one time. great site/life. fundamental research plus the outdoors IIRC.
    how long have you been in Maui, my imperfect memory was that you were living in coastal southern california

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

    LIVE BLOGGING BY ROBERT HELLING
    http://atdotde.blogspot.com/2005/10/others.html

    just saw this a Not Even Wrong
     
    Last edited: Oct 10, 2005
  7. Oct 10, 2005 #6

    Kea

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    Looked at Helling's blog. Smolin's talk sounds like it was very interesting. Do we have any slides for it anywhere? Helling says he said something about twisted ribbons and CPT.
     
  8. Oct 10, 2005 #7

    Kea

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  9. Oct 10, 2005 #8

    marcus

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    glad you found something, Kea. I don't have any leads (judging from the report) about that part of Smolin's talk
     
  10. Oct 10, 2005 #9

    garrett

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    Hey Marcus,

    Your memory is in excellent shape -- it just needs updating. I got my PhD in San Diego about 7 years ago, then moved to Maui to windsurf and do physics on my own. I've been hopping between here, Colorado, and California since -- enjoying life the best I can, while at the same time working on how to get the standard model out of pure geometry.

    Helling's blog entries were a good read -- though they're really just a tease.
     
  11. Oct 12, 2005 #10

    marcus

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    News from the conference

    Here's a Loop Gravity progress report that Lee Smolin posted on Not Even Wrong today, phrased as a response to Robert Helling. He listed a halfdozen or so significant advances, which I have made into a list by spacing so I can focus on them better:
    ------quote------
    Lee Smolin Says:
    October 12th, 2005 at 6:32 am
    Hi, if I can put a comment here I didnt figure out how to put on Robert’s blog:
    Thanks for the comments...We are not afraid of emphasizing open problems but we do hope that people notice when they are solved.
    Hence, I would have hoped you noticed and reported that major progress was described concerning the problem of showing that classical spacetime honestly emerges from background independent theories.
    1. Rovelli derived the graviton propagator and hence Newton’s law.
    2. Freidel and Livine showed in detail that 2+1 quantum gravity with matter has a low energy limit which is an effective QFT on a non-commutative geometry with deformed Poincare invariance. Both results were derived from spin foam models.
    Hence, one can no longer say that there is no understanding of how classical spacetime and low energy qft emerges from these theories.
    There was still more.
    3. Perez showed how regularization ambiguities in the Hamiltonian constraint may be resolved.
    4. Markopoulou discussed a new approach to the low energy limit based on her new paper with Kribs.
    5. Loll announced major results showing that 3+1 spacetime emerges from causal dynamical triangulations and that at short distances the theory scales as a 1+1 dimensional theory.
    6. Livine and Terno showed how to derive the log(area) corrections to black hole entropy and estimate the rate of Hawking radiation.
    7. Starodubtsev reported on work with Freidel in which quantum gravity is defined by a perturbation expansion around a topological quantum field theory where the expansion parameter is G Lambda. This is a very promising direction as there are indications (no proof yet) that this new pert. theory is renormalizable and the low energy limit reproduces QFT in DeSitter spcetime……
    These, and other results were based on detailed calculations and are solid results. I would have hoped that your report would have focused on the presentation of these major result.
    In the face of this kinds of impressive progress, I was not embarrassed to emphasize open issues or speculate a bit about future directions. So my talk was certainly not representative. By the way, I would have thought that as a particle physicist you would have recognized that what I presented was just a preon model. It was translated into the language of LQG with the help of recent work by Bilson-Thompson. This is new stuff and much remains to be done. But you can also no longer say that there is no proposal for unification of matter and geometry in LQG.
    Still to come are new results on rigorous formulations of the theory and at least one striking new results on quantum cosmology, of relevence for upcoming observations.
    ----endquote----
    this is comment #5, currently the most recent comment, at Woit's blog:
    http://www.math.columbia.edu/~woit/wordpress/?p=279#comments
     
    Last edited: Oct 13, 2005
  12. Oct 12, 2005 #11
    marcus, I posted to the general relativity board early today:https://www.physicsforums.com/showthread.php?t=93690

    due to the new guidlines about correct postings, maybe my thread could be removed by a mentor, not for double postings?

    I had considered posting to your loop05, but thought the paper and title was
    not part of the loop talk, great to have all the relevant papers in one place,(here in the loop05) thanks for keeping tabs.
     
  13. Oct 12, 2005 #12

    marcus

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    I thought about it, and I defer to you. I have plenty to think about without this Markopoulou et al paper. And either forum makes sense since there is no sharp division between quantum gravity and general relativity (one is the quantization of the other). So I am editing so as to minimize discussion of the Markopoulou here---whatever there is can go to your thread
     
    Last edited: Oct 13, 2005
  14. Oct 12, 2005 #13
    I'm in Berlin right now and found out that Lee Smolin is giving a public lecture, named "The unfinished revolution: finishing what Einstein started". So how could I resist?

    He started with the question "what is at stake?". Answer: all the big questions (what is time, space, physical law? why is the universe hospitable to life?). After going through the three revolutions (Aristotele, Newton, Einstein) and their notions of space, time, etc., he stressed the importance of relationality in present-day world view, both in qm and gr.

    (He said Leibniz was right about relationality, but he had no workable physical theory, so scientist followed Newton for 200 years. Mach and then Einstein rediscovered relational thinking.)

    So what are the approaches to attack quantum gravity? There are two, according to Smolin.
    1. Einsteins way (rethinking the concepts of space and time, and especially overworking qm)

    2. everybody elses way (string theory, loops, etc.)

    He admitted that he researches everybody elses way, but pointed out the need for radical and rebellious thinking the Einstein way. He also praised Penrose in that context.


    He ended with saying that physicist are standing in the lights and shadows of Einsteins. Lights: Einstein's theories, that they work with. Shadows: neglecting for what is at stake and not sharing Einstein vision of a complete understanding of the universe by rejecting qm.

    Edit: 1. I think Renata Loll was also sitting in the audience.
    2. Smolin was very excited by the coming representation of Winkler and another guy on Friday.
     
    Last edited: Oct 12, 2005
  15. Oct 12, 2005 #14

    marcus

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    Ratzinger, what luck! So glad you were on the scene and could report. Thanks!
    I see that the public talk was at the Urania Science Center in downtown Berlin. sounds like a great venue!
     
    Last edited: Oct 12, 2005
  16. Oct 13, 2005 #15

    marcus

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    here's what that could be about:
    http://loops05.aei.mpg.de/index_files/abstract_winkler.html
    Quantum Black Holes I: Kinematics
    Abstract: We discuss a novel approach to a quantization of spherically symmetric black holes. We present the kinematical setup and focus in particular on a genuinely quantum definition of what a quantum black hole is which avoids fixing classical inputs such as boundaries a priori.

    http://loops05.aei.mpg.de/index_files/abstract_husain.html
    Prof. Viqar Husain
    Quantum Black holes II: Dynamics
    Abstract: I will describe an approach to studying gravitational collapse in quantum gravity. The model studied is the spherically symmetric gravity-scalar system, which is a 2D field theory. An ADM Hamiltonian formalism is utilised, together with an alternative quantisation scheme with similarities to loop quantum gravity. The calculational scheme allows an initial quantum state of matter and metric excitations to be followed to black hole formation, and beyond.

    what paper already posted would correspond most closely to the plannned talks?
    http://www.arxiv.org/abs/gr-qc/0503031
    Flat slice Hamiltonian formalism for dynamical black holes
    V. Husain, O. Winkler
    11 pages
    Phys.Rev. D71 (2005) 104001
    "We give a Hamiltonian analysis of the asymptotically flat spherically symmetric system of gravity coupled to a scalar field. This 1+1 dimensional field theory may be viewed as the 'standard model' for studying black hole physics. Our analysis is adapted to the flat slice Painleve-Gullstrand coordinates. We give a Hamiltonian action principle for this system, which yields an asymptotic mass formula. We then perform a time gauge fixing that gives a Hamiltonian as the integral of a local density. The Hamiltonian takes a relatively simple form compared to earlier work in Schwarzschild gauge, and therefore provides a setting amenable to full quantisation."
     
  17. Oct 13, 2005 #16
    Many thanks for the first hand review!

    Marcus has highlighted the paper authors "other guy".

    It is very interesting that Smolin mentions with praise Penrose?

    It also amazing that "Light + Shade" were mentioned in a specific context?..I have been listening to this:http://www.mikeoldfield.com/flash/light&shade.html

    whilst emerged in some recent books and downloaded papers.

    The Light and Shade music, is playing in "my" background as I delve into scientific foregrounds!

    Thanks again.
     
  18. Oct 13, 2005 #17
    Marcus, I believe this may be of relevance:http://www.arxiv.org/abs/gr-qc/0507088
    and an early paper which I believe your linked paper followed from:http://www.arxiv.org/abs/gr-qc/0210011
    and this:http://www.arxiv.org/abs/gr-qc/0412039
     
  19. Oct 13, 2005 #18
  20. Oct 14, 2005 #19

    marcus

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    did you ever wonder how someone with a name like "Joy Christian" could ever pass peer review? and the paper is being published in Physical Review Letters!

    seriously, thank you for taking care of business on this thread while we are waiting for news from the conference, most likely by the grace of John Baez, may he report soon!

    I have been trying to understand Viqar Husain and Oliver Winkler paper
    http://www.arxiv.org/abs/gr-qc/0503031
    Flat slice Hamiltonian formalism for dynamical black holes
    because in that paper they say they have IN PREPARATION one which probably they will deliver tomorrow at the conference.

    the one in preparation is not yet available of course, they saved it for the conference. It is called
    Quantum Hamiltonian for dynamical black holes
     
    Last edited: Oct 14, 2005
  21. Oct 14, 2005 #20

    marcus

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    Ratzinger, I see that your biography shows you won the Nobel prize in 2009. What was it in? I hope physics and not something dumb like economics.

    Why are you always in Acapulco when the night clubs are better in Berlin?
     
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