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Ideas for first quarter 2009 most important paper (nominations)

  1. Mar 17, 2009 #1

    marcus

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    Here our last MIP poll:
    https://www.physicsforums.com/showthread.php?t=282166

    By the end of this month I'd like to have a short list of promising first quarter papers. Ones that appeared Jan-March 2009 and stand a good chance of turning out to be important or valuable for future research.

    That's something we will be able to gauge approximately in six months or a year from now, just by checking the citations, and also our subjective judgment will be clearer in retrospect.

    But for now it's difficult if not impossible to be sure. We can only guess. One thing that interests me is who the good guessers are. In the last MIP poll, if we go by the citation counts accumulated so far, one of friend's guesses turned out way ahead of the rest (it now has 16 cites compare with 4 for the next highest.)

    So which of the first quarter (nonstring QG) papers get nominated? I have four to suggest at the moment.

    Conrady Freidel http://arxiv.org/abs/0902.0351
    Barrett et al http://arxiv.org/abs/0902.1170
    Bonzom http://arxiv.org/abs/0903.0267
    Marugan et al http://arxiv.org/abs/0902.0697

    There is also a paper by Claudio Perini and Elena Magliaro that is in the works and could appear soon. If it appears this quarter I woud definitely include it. Perini presented the results at this Perimeter talk here:
    http://pirsa.org/09020023/
    Maybe the video, audio, and pdf files here can serve as a place-holder for that paper
    Graviton propagator from EPRL spinfoam model
    Claudio Perini
    "We derive geometric correlation functions in the new spinfoam model with coherent states techniques, making connection with quantum Regge calculus and perturbative quantum gravity. In particular we recover the expected scaling with distance for all components of the propagator. We expect the same technique to be well-suited for other spinfoam models."

    It's an impressive talk. One of the things that persuades me the LQG low energy thing will be pretty much wrapped up by the time Rovelli lectures on it at the Corfu school.
     
    Last edited: Mar 18, 2009
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  3. Mar 18, 2009 #2

    MTd2

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  4. Mar 18, 2009 #3

    marcus

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    That's actually a very interesting suggestion, MTd2!
    Just so other readers can see what we are talking about, I will copy from Oriti's conclusion paragraph:
    =quote=
    We have presented a new GFT/spin foam model for 4d quantum gravity. It is based on a recent extension of the GFT formalism, in which the field depends on both group and Lie algebra variables, representing the discrete analogue of the variables in a BF-like formulation of gravity.

    The new model allows a straightforward implementation of the simplicity constraints that give gravity from BF theory, and has quantum amplitudes with the explicit form of simplicial path integrals for 1st order gravity. In doing so it sidesteps some ambiguous aspects of the usual spin foam quantization procedure. The geometric interpretation of the variables and of the different contributions to the quantum amplitudes is also made manifest.

    Moreover, thanks to the links with other discrete approaches to quantum gravity, that we have explicitly shown, its usefulness and interest may well extend beyond the spin foam or loop quantum gravity framework.

    While there are still several aspects of the new model that should be analyzed further, and interesting variations of the construction leading to it that can be considered, we believe that the new model represents an altogether new approach to the spin foam quantization of gravity and opens up a whole landscape possible new developments.

    =endquote=

    Since it is still too soon to tell if the new GFT can succeed, let's look for indications of how it is being received in the wider LQG community.

    We know that Oriti has been awarded a large EU young researchers prize and a postdoc position at the Albert Einstein Institute, where he can use some of the prize money to set up his own research group and bring together a few other QG researchers of his generation. This is already unusual. He only got his PhD in around 2004 as I recall. It had a funny quote from Groucho Marx as the epigraph, as I recall. I have always been curious about Oriti.

    What else do we know? Is he one of the invited speakers at Loops 09?

    Wow! Look at this
    http://www.loops09.org/School/School-en.htm [Broken]
    He is one of 5 people invited to lecture at the weeklong Loops 09 Prep school. Yongge Ma obviously wants to get his grad students and postdocs into GFT research. The other lecturers are older more established folks, major figures. (Rovelli, Thiemann, Bojowald, Williams). Actually Ruth Williams is the world top expert on Regge calculus (the root of simplicial QG) and she was Oriti's thesis advisor at Cambridge! There is a family connection in the school lineup.

    Notice that Yongge Ma did not get Loll. I think he is in effect betting that GFT will bridge LQG together with Simplicial (ie Regge) quantum gravity. So that ultimately LQG+Simplicial will duplicate the successes of Loll's CDT and will have more growth potential. That puts Oriti (as the main promoter of GFT) in a key role.

    OK so you are alerting me to this Oriti paper. It has a very new kind of GFT. Instead of just defining the field on the cartesian of many copies of the group G, it is using G+g, the group AND its Lie Algebra. Do I understand right? Is a field being defined on the cartesian product of multiple copies of G+g?
     
    Last edited by a moderator: May 4, 2017
  5. Mar 19, 2009 #4

    atyy

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  6. Mar 19, 2009 #5

    marcus

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    I think the main Horava paper---one I was considering anyway---is this January paper:
    http://arxiv.org/abs/0901.3775

    The January paper gives a detailed description of what he's talking about. The approach is 4D and moderately background independent in the sense LQG and CDT people use the term.
    Setup without using a prior designated metric.
    He only breaks background independence in a mild way by fixing the topology and assuming a foliation---but CDT also has essentially the same reliance on a foliation, or time-slicing.

    The March paper you mention is a shorter one whose main result, as far as I can see, is just to point out that Horava's January QG (of arxiv 0901.3775) has the same interesting running of dimensionality from 4D down to 2D that Ambjorn Jurkiewicz Loll found in 2005 using CDT. (also noticed in Asymptotic Safe gravity and later in Loop). That's interesting but it's not self-contained--it refers back to the main paper.

    His January QG approach belongs in the background independent 4D group. So maybe we should add it to our poll. Sometimes I've put pairs of papers on as choices but this time as of now, if I were to choose, I'd put just 0901.3775
     
  7. Mar 19, 2009 #6

    atyy

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    Yes, the earlier Horava paper is better for the poll. I wrongly thought it had come out late last year and wasn't qualified for the first quarter.
     
  8. Mar 19, 2009 #7

    marcus

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    Thanks for suggesting we pick up on Horava's 4D quantum gravity! Maybe it is time to list nominee titles. Some may have to be winnowed out later.

    http://arxiv.org/abs/0902.0351
    Quantum geometry from phase space reduction
    Florian Conrady, Laurent Freidel
    31 pages, 1 figure
    'In this work we give an explicit isomorphism between the usual spin network basis and the direct quantization of the reduced phase space of tetrahedra. The main outcome is a formula that describes the space of SU(2) invariant states by an integral over coherent states satisfying the closure constraint exactly, or equivalently, as an integral over the space of classical tetrahedra. This provides an explicit realization of theorems by Guillemin--Sternberg and Hall that describe the commutation of quantization and reduction. In the final part of the paper, we use our result to express the FK spin foam model as an integral over classical tetrahedra and the asymptotics of the vertex amplitude is determined."

    http://arxiv.org/abs/0902.1170
    Asymptotic analysis of the EPRL four-simplex amplitude
    John W. Barrett, Richard J. Dowdall, Winston J. Fairbairn, Henrique Gomes, Frank Hellmann
    "An asymptotic formula for a certain 4d Euclidean spin foam 4-simplex amplitude is given for the limit of large spins. The analysis covers the model with Immirzi parameter less than one defined separately by Engle, Livine, Pereira and Rovelli (EPRL) and Freidel and Krasnov (FK). We are also able to analyse the EPRL model with Immirzi parameter greater than one. The asymptotic formula has one term which is proportional to the cosine of the Regge action for gravity, and it is shown that this term is present whenever the boundary data determines a non-degenerate Euclidean geometry for the 4-simplex. A scheme for resolving the phase ambiguity of the boundary data in these cases is also presented."

    Bonzom http://arxiv.org/abs/0903.0267
    From lattice BF gauge theory to area-angle Regge calculus
    Valentin Bonzom
    18 pages, 2 figures
    "We consider Riemannian 4d BF lattice gauge theory, on a triangulation of spacetime. Introducing the simplicity constraints which turn BF theory into simplicial gravity, some geometric quantities of Regge calculus, areas, and 3d and 4d dihedral angles, are identified. The parallel transport conditions are taken care of to ensure a consistent gluing of simplices. We show that these gluing relations, together with the simplicity constraints, contain the constraints of area-angle Regge calculus in a simple way, via the group structure of the underlying BF gauge theory. This provides a precise road from constrained BF theory to area-angle Regge calculus. Doing so, a framework combining variables of lattice BF theory and Regge calculus is built. The action takes a form à la Regge and includes the contribution of the Immirzi parameter. In the absence of simplicity constraints, the standard spin foam model for BF theory is recovered. Insertions of local observables are investigated, leading to Casimir insertions for areas and 6j-symbols for 3d angles. The present formulation is argued to be suitable for deriving spin foam models from discrete path integrals.

    http://arxiv.org/abs/0902.3903
    Group field theory and simplicial quantum gravity (MTd2 suggestion)
    Daniele Oriti
    (Submitted on 23 Feb 2009)
    "We present a new Group Field Theory for 4d quantum gravity. It incorporates the constraints that give gravity from BF theory, and has quantum amplitudes with the explicit form of simplicial path integrals for 1st order gravity. The geometric interpretation of the variables and of the contributions to the quantum amplitudes is manifest. This allows a direct link with other simplicial gravity approaches, like quantum Regge calculus, in the form of the amplitudes of the model, and dynamical triangulations, which we show to correspond to a simple restriction of the same."

    http://pirsa.org/09020023/
    Graviton propagator from EPRL spinfoam model
    Claudio Perini, Elena Magliaro (this is a placeholder in case their paper comes out before April)

    http://arxiv.org/abs/0901.3775
    Quantum Gravity at a Lifgarbagez Point (atyy suggestion)
    Petr Horava
    29 pages
    "We present a candidate quantum field theory of gravity with dynamical critical exponent equal to z=3 in the UV. (As in condensed matter systems, z measures the degree of anisotropy between space and time.) This theory, which at short distances describes interacting nonrelativistic gravitons, is power-counting renormalizable in 3+1 dimensions. When restricted to satisfy the condition of detailed balance, this theory is intimately related to topologically massive gravity in three dimensions, and the geometry of the Cotton tensor. At long distances, this theory flows naturally to the relativistic value z=1, and could therefore serve as a possible candidate for a UV completion of Einstein's general relativity or an infrared modification thereof. The effective speed of light, the Newton constant and the cosmological constant all emerge from relevant deformations of the deeply nonrelativistic z=3 theory at short distances."

    http://arxiv.org/abs/0902.0697
    Big Bounce and inhomogeneities
    David Brizuela, Guillermo A. Mena Marugan, Tomasz Pawlowski
    4 pages, 2 figures
    "The dynamics of an inhomogeneous universe is studied with the methods of Loop Quantum Cosmology as an example of the quantization of vacuum cosmological spacetimes containing gravitational waves (Gowdy spacetimes). The analysis performed at the effective level shows that: (i) The initial Big Bang singularity is replaced (as in the case of homogeneous cosmological models) by a Big Bounce, joining deterministically two large universes, (ii) the universe size at the bounce is at least of the same order of magnitude as that of the background homogeneous universe, (iii) for each gravitational wave mode, the difference in amplitude at very early and very late times has a vanishing statistical average when the bounce dynamics is strongly dominated by the inhomogeneities, whereas this average is positive when the dynamics is in a near-vacuum regime, so that statistically the inhomogeneities are amplified."
     
    Last edited: Mar 19, 2009
  9. Mar 19, 2009 #8

    MTd2

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    There is this guy, with lots of topcited papers, Dirk Kreimer, who collaborates with Allan Connes. In the last five years he noticed some kinds of patterns in the perturbative expantion of GR. This quarter he had somekind of breakthrough that is going to lead to see explicitely, that is, prove, how gravity can be renormilzable. It seems his results agrees with assymptotic safety, except that now, this could lead to an algebraic proof not a "mere" lattice or computational evidence.

    These are the papers:

    http://arxiv.org/pdf/0903.2849

    http://arxiv.org/pdf/0902.1223

    For a perspective of their importance, look at his paper http://arxiv.org/abs/0805.4545. To see how all this relates to assymptotic safety, see section 3.2.2.

    Well, to tell you the truth, I don't understand his formalism yet, but to learn about it, look at http://math.bu.edu/people/dkreimer/structure.html.

    Interstingly, it seems his approach could end up linking quantum gravity (via dario benedetti) and string theory. And also relate them to twistors, supergravity, ADS/CFT, assymptotic safety,and mainly, Conne's non commutative physics.

    I don't know if that is true, but it's the impression I get. But I need confirmation from you guys. Interesting, if that is the case, don't you think?
     
  10. Mar 21, 2009 #9

    MTd2

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    Marcuuuuuuuuuuusssssssssssssss

    say somethin!!! :cry:
     
  11. Mar 21, 2009 #10

    marcus

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    Heh.

    Well folks there are 10 more days to go before we need to finalize, and I count 9 papers that have been suggested. And there has been no discussion of the papers (or a very little bit in a couple of cases) which is fine with me either way. We can discuss everybody's nominations or not.

    Personally I am still hoping that one or more really good paper will get posted on arxiv in the next 9 or 10 days.
     
  12. Mar 22, 2009 #11

    marcus

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    http://arxiv.org/abs/0903.3475
    4d Deformed Special Relativity from Group Field Theories
    Florian Girelli, Etera R. Livine, Daniele Oriti
    23 pages
    (Submitted on 20 Mar 2009)
    "We derive a scalar field theory of the deformed special relativity type, living on non-commutative kappa-Minkowski spacetime and with a kappa-deformed Poincare symmetry, from the SO(4,1) group field theory defining the transition amplitudes for topological BF-theory in 4 space-time dimensions. This is done at a non-perturbative level of the spin foam formalism working directly with the group field theory (GFT). We show that matter fields emerge from the fundamental model as perturbations around a specific phase of the GFT, corresponding to a solution of the fundamental equations of motion, and that the non-commutative field theory governs their effective dynamics."

    This result is very good news. This was done for 3D in 2005 by Freidel and Livine and others. Then it seemed as if DSR got stuck after 2006, and could not extend the result to 4D.

    The corresponding papers for 3D gravity are:
    http://arXiv.org/abs/hep-th/0502106
    Ponzano-Regge model revisited III: Feynman diagrams and Effective field theory

    http://arXiv.org/abs/hep-th/0512113
    3d Quantum Gravity and Effective Non-Commutative Quantum Field Theory


    We certainly should put this one on the MIP poll for first-quarter 2009.

    Here is a quote from the conclusions section of today's paper by Girelli, Livine, Oriti.
    ==quote==
    Not only this is the first example of a derivation of a DSR model for matter from a more fundamental quantum gravity model, and one further link
    between non-commutative geometry and quantum gravity formulated in terms of spin foam/loop quantum gravity ideas, but it is of great interest from the point of view of quantum gravity phenomenology, as we have pointed out in the introduction. It represents, in fact, another possible way of bridging the gap between quantum gravity at Planck scale and effective (and testable) physics at low energies.
    ==endquote==
     
    Last edited: Mar 22, 2009
  13. Mar 26, 2009 #12

    MTd2

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  14. Mar 26, 2009 #13
  15. Mar 31, 2009 #14

    MTd2

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    This contest shouldve finished yesterday!
     
  16. Mar 31, 2009 #15

    marcus

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    For convenience, I have arbitrarily chosen one author's name as a recognizable tag to designate each of the papers. The name chosen was not necessarily meant to signify a principal author.
    Several of these papers were proposed by MTd2, atyy, and maybe by other PF posters. Thanks for the help! I have narrowed down the list some so as not to make the poll too big.
    Loop quantum cosmology of Bianchi I models (Ashtekar et al)
    Asymptotic analysis of the EPRL four-simplex amplitude (Barrett et al)
    Taming perturbative divergences in asymptotically safe gravity (Benedetti et al)
    Particle Topology, Braids, and Braided Belts (Bilson-Thompson et al)
    From lattice BF gauge theory to area-angle Regge calculus (Bonzom)
    Quantum geometry from phase space reduction (Freidel et al)
    Quantum Gravity at a Lifgarbagez Point (Horava)
    4d Deformed Special Relativity from Group Field Theories (Livine et al)
    Group field theory and simplicial quantum gravity (Oriti)
    Disordered Locality as an Explanation for the Dark Energy (Smolin et al)

    Ashtekar et al
    http://arxiv.org/abs/0903.3397
    Loop quantum cosmology of Bianchi I models
    Abhay Ashtekar, Edward Wilson-Ewing
    (Submitted on 19 Mar 2009)
    "The 'improved dynamics' of loop quantum cosmology is extended to include anisotropies of the Bianchi I model. As in the isotropic case, a massless scalar field serves as a relational time parameter. However, the extension is non-trivial because one has to face several conceptual subtleties as well as technical difficulties. These include: a better understanding of the relation between loop quantum gravity (LQG) and loop quantum cosmology (LQC); handling novel features associated with the non-local field strength operator in presence of anisotropies; and finding dynamical variables that make the action of the Hamiltonian constraint manageable. Our analysis provides a conceptually complete description that overcomes limitations of earlier works. We again find that the big bang singularity is resolved by quantum geometry effects but, because of the presence of Weyl curvature, Planck scale physics is now much richer than in the isotropic case. Since the Bianchi I models play a key role in the Belinskii, Khalatnikov, Lifgarbagez (BKL) conjecture on the nature of generic space-like singularities in general relativity, the quantum dynamics of Bianchi I cosmologies is likely to provide considerable intuition about the fate of generic space-like singularities in quantum gravity. Finally, we show that the quantum dynamics of Bianchi I cosmologies projects down exactly to that of the Friedmann model. This opens a new avenue to relate more complicated models to simpler ones, thereby providing a new tool to relate the quantum dynamics of LQG to that of LQC."

    Barrett et al
    http://arxiv.org/abs/0902.1170
    Asymptotic analysis of the EPRL four-simplex amplitude
    John W. Barrett, Richard J. Dowdall, Winston J. Fairbairn, Henrique Gomes, Frank Hellmann
    "An asymptotic formula for a certain 4d Euclidean spin foam 4-simplex amplitude is given for the limit of large spins. The analysis covers the model with Immirzi parameter less than one defined separately by Engle, Livine, Pereira and Rovelli (EPRL) and Freidel and Krasnov (FK). We are also able to analyse the EPRL model with Immirzi parameter greater than one. The asymptotic formula has one term which is proportional to the cosine of the Regge action for gravity, and it is shown that this term is present whenever the boundary data determines a non-degenerate Euclidean geometry for the 4-simplex. A scheme for resolving the phase ambiguity of the boundary data in these cases is also presented."

    Benedetti et al
    http://arxiv.org/abs/0902.4630
    Taming perturbative divergences in asymptotically safe gravity
    Dario Benedetti, Pedro F. Machado, Frank Saueressig
    16 pages
    (Submitted on 26 Feb 2009)
    "We use functional renormalization group methods to study gravity minimally coupled to a free scalar field. This setup provides the prototype of a gravitational theory which is perturbatively non-renormalizable at one-loop level, but may possess a non-trivial renormalization group fixed point controlling its UV behavior. We show that such a fixed point indeed exists within the truncations considered, lending strong support to the conjectured asymptotic safety of the theory. In particular, we demonstrate that the counterterms responsible for its perturbative non-renormalizability have no qualitative effect on this feature."

    Bilson-Thompson et al
    http://arxiv.org/abs/0903.1376
    Particle Topology, Braids, and Braided Belts
    Sundance Bilson-Thompson, Jonathan Hackett, Louis H. Kauffman
    21 pages, 16 figures
    (Submitted on 7 Mar 2009)
    "Recent work suggests that topological features of certain quantum gravity theories can be interpreted as particles, matching the known fermions and bosons of the first generation in the Standard Model. This is achieved by identifying topological structures with elements of the framed Artin braid group on three strands, and demonstrating a correspondence between the invariants used to characterise these braids (a braid is a set of non-intersecting curves, that connect one set of N points with another set of N points), and quantities like electric charge, colour charge, and so on. In this paper we show how to manipulate a modified form of framed braids to yield an invariant standard form for sets of isomorphic braids, characterised by a vector of real numbers. This will serve as a basis for more complete discussions of quantum numbers in future work."

    Bonzom
    http://arxiv.org/abs/0903.0267
    From lattice BF gauge theory to area-angle Regge calculus
    Valentin Bonzom
    18 pages, 2 figures
    "We consider Riemannian 4d BF lattice gauge theory, on a triangulation of spacetime. Introducing the simplicity constraints which turn BF theory into simplicial gravity, some geometric quantities of Regge calculus, areas, and 3d and 4d dihedral angles, are identified. The parallel transport conditions are taken care of to ensure a consistent gluing of simplices. We show that these gluing relations, together with the simplicity constraints, contain the constraints of area-angle Regge calculus in a simple way, via the group structure of the underlying BF gauge theory. This provides a precise road from constrained BF theory to area-angle Regge calculus. Doing so, a framework combining variables of lattice BF theory and Regge calculus is built. The action takes a form à la Regge and includes the contribution of the Immirzi parameter. In the absence of simplicity constraints, the standard spin foam model for BF theory is recovered. Insertions of local observables are investigated, leading to Casimir insertions for areas and 6j-symbols for 3d angles. The present formulation is argued to be suitable for deriving spin foam models from discrete path integrals."

    Freidel et al
    http://arxiv.org/abs/0902.0351
    Quantum geometry from phase space reduction
    Florian Conrady, Laurent Freidel
    31 pages, 1 figure
    "In this work we give an explicit isomorphism between the usual spin network basis and the direct quantization of the reduced phase space of tetrahedra. The main outcome is a formula that describes the space of SU(2) invariant states by an integral over coherent states satisfying the closure constraint exactly, or equivalently, as an integral over the space of classical tetrahedra. This provides an explicit realization of theorems by Guillemin--Sternberg and Hall that describe the commutation of quantization and reduction. In the final part of the paper, we use our result to express the FK spin foam model as an integral over classical tetrahedra and the asymptotics of the vertex amplitude is determined."

    Horava
    http://arxiv.org/abs/0901.3775
    Quantum Gravity at a Lifgarbagez Point
    Petr Horava
    29 pages
    "We present a candidate quantum field theory of gravity with dynamical critical exponent equal to z=3 in the UV. (As in condensed matter systems, z measures the degree of anisotropy between space and time.) This theory, which at short distances describes interacting nonrelativistic gravitons, is power-counting renormalizable in 3+1 dimensions. When restricted to satisfy the condition of detailed balance, this theory is intimately related to topologically massive gravity in three dimensions, and the geometry of the Cotton tensor. At long distances, this theory flows naturally to the relativistic value z=1, and could therefore serve as a possible candidate for a UV completion of Einstein's general relativity or an infrared modification thereof. The effective speed of light, the Newton constant and the cosmological constant all emerge from relevant deformations of the deeply nonrelativistic z=3 theory at short distances."

    Livine et al
    http://arxiv.org/abs/0903.3475
    4d Deformed Special Relativity from Group Field Theories
    Florian Girelli, Etera R. Livine, Daniele Oriti
    23 pages
    (Submitted on 20 Mar 2009)
    "We derive a scalar field theory of the deformed special relativity type, living on non-commutative kappa-Minkowski spacetime and with a kappa-deformed Poincare symmetry, from the SO(4,1) group field theory defining the transition amplitudes for topological BF-theory in 4 space-time dimensions. This is done at a non-perturbative level of the spin foam formalism working directly with the group field theory (GFT). We show that matter fields emerge from the fundamental model as perturbations around a specific phase of the GFT, corresponding to a solution of the fundamental equations of motion, and that the non-commutative field theory governs their effective dynamics."

    Oriti
    http://arxiv.org/abs/0902.3903
    Group field theory and simplicial quantum gravity
    Daniele Oriti
    (Submitted on 23 Feb 2009)
    "We present a new Group Field Theory for 4d quantum gravity. It incorporates the constraints that give gravity from BF theory, and has quantum amplitudes with the explicit form of simplicial path integrals for 1st order gravity. The geometric interpretation of the variables and of the contributions to the quantum amplitudes is manifest. This allows a direct link with other simplicial gravity approaches, like quantum Regge calculus, in the form of the amplitudes of the model, and dynamical triangulations, which we show to correspond to a simple restriction of the same."

    Smolin et al
    http://arxiv.org/abs/0903.5303
    Disordered Locality as an Explanation for the Dark Energy
    Chanda Prescod-Weinstein, Lee Smolin
    12 pages
    (Submitted on 30 Mar 2009)
    "We discuss a novel explanation of the dark energy as a manifestation of macroscopic non-locality coming from quantum gravity, as proposed by Markopoulou. It has been previously suggested that in a transition from an early quantum geometric phase of the universe to a low temperature phase characterized by an emergent spacetime metric, locality might have been 'disordered'. This means that there is a mismatch of micro-locality, as determined by the microscopic quantum dynamics and macro-locality as determined by the classical metric that governs the emergent low energy physics. In this paper we discuss the consequences for cosmology by studying a simple extension of the standard cosmological models with disordered locality. We show that the consequences can include a naturally small vacuum energy."
     
    Last edited: Mar 31, 2009
  17. Mar 31, 2009 #16

    MTd2

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  18. Mar 31, 2009 #17

    MTd2

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    http://arxiv.org/abs/0903.5080


    From the article.

    "The remarkable aspect of (23) is that, perhaps for the first time since Bekenstein’s pioneering work, one has an ab initio computation of SIH and obtained an infinite series, asymptotic in AIH, of quantum spacetime fluctuation corrections to the Bekenstein-Hawking area law; each term of this series is finite and unambiguously calculable. The leading correction to the area law is logarithmic and has what appears to be a robust coefficient. With due modesty, one may say that these corrections are the only known physical signatures
    of loop quantum gravity as applied to the computation of microcanonical black
    hole entropy."

    Don't you think this is relevant? :eek:
     
  19. Mar 31, 2009 #18

    marcus

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    I decided to keep the main list down to ten papers. This allows for some write-ins.
     
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