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Oriti's new book! Cambridge (2006) Towards Quantum Gravity

  1. Dec 10, 2005 #1

    marcus

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    Oriti's new book! Cambridge (2006) "Towards Quantum Gravity"

    Daniele Oriti is a really nice young person as well as being on the frontline of QG research. He is at Cambridge
    His PhD thesis contained ground-breaking quotations from Homer Simpson and Groucho Marx.

    the important thing is that he writes simply and lucidly and in a not too compressed way---so you can learn from his explanations without too much pain.

    Cambridge University Press has given Oriti the responsibility of assembling and editing a very necessary book. We should have had this book all along. It has been sorely missed. You can tell from the title, which is exactly the right title:

    [1] D. Oriti, editor, Towards quantum gravity: different approaches to a new understanding of space and time, Cambridge University Press (2006)

    thank God that is finally in the works.

    the point is that there ARE a number of new (non-string) approaches moving towards a quantum theory of spacetime---and they are beginning to uncover a really new picture of spacetime.

    Prominent among these are Renate Loll triangulations and Martin Reuter renormalizable QG. but there is a lot of new activity in spinfoams too (Christensen, Freidel----GFT "group field theory", also Rovelli and Smolin both embarked on fresh initiatives)

    so there is a lot of ferment, and inventiveness, just now---and we really need a clearly written book that keeps track of what is going on

    I first heard about this Oriti book in a paper which Oriti just posted this week.
    http://arxiv.org/abs/gr-qc/0512048
    Quantum gravity as a group field theory: a sketch
    Daniele Oriti
    jpconf; 8 pages, 9 figures; to appear in the Proceedings of the Fourth Meeting on Constrained Dynamics and Quantum Gravity, Cala Gonone, Italy, September 12-16, 2005
    DAMTP-2005-123
    "We give a very brief introduction to the group field theory approach to quantum gravity, a generalisation of matrix models for 2-dimensional quantum gravity to higher dimension, that has emerged recently from research in spin foam models."

    My comment is that even though Laurent Freidel is the main developer of GFT as applied to QG (also Krasnov and their co-authors) I find it easier to read about GFT from Oriti. Freidel has a lean mathematical style.
     
    Last edited: Dec 10, 2005
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  3. Dec 10, 2005 #2

    marcus

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    here is Oriti's homepage at Cambridge. It has a good snapshot of him on vacation.

    http://www.damtp.cam.ac.uk/user/do001/

    for contrast, here is Lee Smolin's snapshot of Daniele Oriti with John Barrett (the Barrett-Crane spinfoam model) and Julian Barbour

    http://math.ucr.edu/home/baez/marseille/oriti_barrett_barbour.jpg

    this was at the May 2004 marseille QG conference

    here he is with Alejandro Perez (another young QG researcher working in spinfoam)

    http://math.ucr.edu/home/baez/marseille/oriti_perez.jpg
     
    Last edited: Dec 10, 2005
  4. Dec 10, 2005 #3

    marcus

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    Last edited: Dec 10, 2005
  5. Dec 13, 2005 #4

    marcus

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    One of the chapters of Oriti's book has appeared. It was written by Gambini and Pullin.
    I mentioned it here:
    https://www.physicsforums.com/showthread.php?p=854977#post854977
    It looks like Oriti is interesting in constructing a unifying framework for several different approaches to quantum gravity. He just posted a new paper,
    http://arxiv.org/abs/gr-qc/0512069
    and there was something in it about this:
    ---quote---
    Finally, we have shown how the vertex amplitudes for the generalised group field theory with causality restrictions are given by complex functions of the variables of the theory, with an expression very closely related to the exponential of the Regge action for simplicial gravity, thus hinting to an expression of this type for the complete Feynman graph amplitudes.
    If this is verified, maybe for slightly different choices of the group field theory action, the nature of the models will be manifestly that of a simplicial third quantization of gravity and the generalised formalism will be naturally understood as a unified framework for as different approaches to non-perturbative quantum gravity as loop quantum gravity, spin foam models, quantum Regge calculus and dynamical triangulations, and one would be left to study in detail how each of them can be obtained and understood within the generalised formalism.
    ---endquote---
    so he wants to join the spinfoam with the triangulations
    then whatever can be done with Loll gravity can also be done with loop, or with spinfoam. and vice versa.
    Here is the abstract of this new paper:
    http://arxiv.org/abs/gr-qc/0512069
    Generalised group field theories and quantum gravity transition amplitudes
    Daniele Oriti
    6 pages, 2 figures
    DAMTP-2005-127
    "We construct a generalised formalism for group field theories, in which the domain of the field is extended to include additional proper time variables, as well as their conjugate mass variables. This formalism allows for different types of quantum gravity transition amplitudes in perturbative expansion, and we show how both causal spin foam models and the usual a-causal ones can be derived from it, within a sum over triangulations of all topologies. We also highlight the relation of the so-derived causal transition amplitudes with simplicial gravity actions."
     
  6. Dec 14, 2005 #5

    garrett

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    This is going to sound funny, but I think the new book marcus is excited about is actually better represented by Oriti's thesis:
    http://arxiv.org/pdf/gr-qc/0311066
    I spent all of today reading it and it's a damn impressive survey and unification of most recent approaches to quantum gravity. My impression is that he has been a sponge, soaking up all the wisdom and current goings on from leaders in the field, distilling it, and wringing himself out into his thesis. It's quite far reaching in scope. I'd recommend it as a good companion volume to Rovelli's book, which is more focused on a particular approach.

    I expect Oriti's book, on the other hand, will mostly be a typical compilation of other's papers. But you can bet it will have a very good intro by Oriti.
     
  7. Dec 15, 2005 #6

    marcus

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    I'm convinced
    :smile:
    what we really need is an update of Oriti's thesis, not a compilation of different authors each with their own style.
    something like those first 40 or 60 pages of the thesis where he summarizes all the different kyugees. maybe in fact the intro to the new book.
    I'm sleepy so I'm going to turn in
     
  8. Dec 19, 2005 #7

    marcus

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    https://www.physicsforums.com/showthread.php?p=860703#post860703

    Oriti just posted a chapter he is contributing to another QG book
    this time it is a Swiss publisher.


    http://arxiv.org/abs/gr-qc/0512103
    Quantum Gravity as a quantum field theory of simplicial geometry
    Daniele Oriti
    23 pages, 13 figures; to be published in 'Mathematical and Physical Aspects of Quantum Gravity', B. Fauser, J. Tolksdorf and E. Zeidler eds, Birkhaeuser, Basel (2006)
    "This is an introduction to the group field theory approach to quantum gravity, with emphasis on motivations and basic formalism, more than on recent results; we elaborate on the various ingredients, both conceptual and formal, of the approach, giving some examples, and we discuss some perspectives of future developments."

    lot of QG books in the works----nonstring QG getting established.
    people seem to be asking Oriti to write

    Cambridge UP gave him the job of editing "Towards QG", a collection of papers representing different approaches to GQ, and now this editors of this Swiss book "Mathematical Physical Aspects of QG" have asked him to write a chapter on the Group Field approach to QG.
     
  9. Feb 15, 2006 #8

    marcus

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    Polchinski and Horowitz contribution to Oriti's book

    http://arxiv.org/abs/gr-qc/0602037
    Gauge/gravity duality
    Gary T. Horowitz, Joseph Polchinski
    To appear in "Towards quantum gravity", ed. Daniele Oriti, Cambridge University Press. 20pgs
    "We review the emergence of gravity from gauge theory in the context of AdS/CFT duality. We discuss the evidence for the duality, its lessons for gravitational physics, generalizations, and open questions."

    Sample quotes

    3rd paragraph on page 17
    "In summary, we see convincing reason to place AdS/CFT duality in the category of true but not proven. Indeed, we regard it on much the same footing as such mathematical conjectures as the Riemann hypothesis. Both provide unexpected connections between seemingly different structures (and speaking as physicists we find a connection between gauge theory and gravity even more fascinating than one between prime numbers and analytic functions), and each has resisted either proof or disproof in spite of concentrated attention. In either case it may be that the final proof will be narrow and uninstructive, but it seems more likely that the absence of a proof points to the existence of important new concepts to be found. "

    first paragraph of introduction, page 1

    "Assertion: Hidden within every non-Abelian gauge theory, even within the weak and strong nuclear interactions, is a theory of quantum gravity. This is one implication of AdS/CFT duality. It was discovered by a circuitous route, involving in particular the relation between black branes and D-branes in string theory. It is an interesting exercise, however, to first try to find a path from gauge theory to gravity as directly as possible.

    Thus let us imagine that we know a bit about gauge theory and a bit about gravity but nothing about string theory, and ask, how are we to make sense of the assertion?"

    BTW Laurent Freidel has a paper in preparation called something like "Quantum gravity hidden in Feynman diagrams. Perhaps the theory of quantum gravity which everyone is looking for is hidden somewhere in the theory of matter and will be obvious when it is finally recognized:smile:

    Anyway, Oriti could be assembling a provocative book. I am glad that Cambridge press has authorized him to do it.
     
  10. Feb 19, 2006 #9
    Oops. You just stepped into a big stinky pile of strings :biggrin:
     
  11. Feb 20, 2006 #10

    selfAdjoint

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    I am really doubtful whether the status of AdS/CFT duality is comparable to that of the Riemann Hypothesis. Note that the mass gap of Yang-Mills theory, which underlies all gauge theory, is a Clay Problem, and still unsoved. But I do acknowledge that the consequences they specify are marvelous, if true: that inside every gauge theory, even QED, lies a theory of quantum gravity. I would love to see how this is derived, if anyone has improved on the "circuitous route".
     
  12. Feb 20, 2006 #11
    None of the multitude of consistency checks have contradicted ads/cft so I do think the attitude of researchers to assume it's true and continue to study it's implications if correct is justified.

    The U(1) gauge group of QED isn`t large enough for it to be dual to a higher dimensional quantum theory of gravity. In ads/cft it's the much larger maximally supersymmetric N=4 yang mills gauge group that is dual to the gravitational sector of ads.
     
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