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Loops 2013 talks

  1. Jul 5, 2013 #1

    marcus

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    Loops 2013 opens at Perimeter a couple of weeks from now and abstracts of some of the invited talks have been posted. Reading the abstracts can give an idea of the main trends in current QG research. It's also interesting to see who the invited speakers from outside are and what they will be talking about. There's a pattern for Loops conference organizers to invite plenary talks by a selection of people from neighboring fields (CDT, string, AsymSafe, ShapeDyn, cosmology&observational tests). It can be informative to see which particular topics the Loop researchers currently want most to hear about or engage with.

    It's also true that one of the invited speakers is a longtime PF member, who has contributed quite a bunch of interesting posts to this BtSM forum, so you might want to check the abstract and see what that speaker will be talking about.

    I thought the emphasis on cosmology (including observational and testing) was significant. I'll post some abstracts of invited talks and then give the list of plenary speakers as it stands so far.
     
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  3. Jul 5, 2013 #2

    marcus

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    Ivan Agullo, DAMTP Cambridge
    A Quantum Gravity Extension of the Inflationary Scenario
    Since the standard inflationary paradigm is based on quantum field theory on classical space-times, it excludes the Planck era. Using techniques from loop quantum gravity, the theory is extended to overcome this limitations. The new framework sharpens conceptual issues by distinguishing between the true and apparent trans-Planckian difficulties and provides sufficient conditions under which the true difficulties can be overcome within a quantum gravity theory, with interesting lessons for both theory and observations.

    Abhay Ashtekar, Pennsylvania State University
    Promising Paths
    In LQG we work in the spirit of Antonio Machado: "Traveler, there is no path; Paths are made by walking." I will present a bird's eye view of some of the paths that have emerged since Loops 11 and offer a few suggestions.

    Aurelien Barrau, Universite Joseph Fourier
    Some possible ways to observe consequences of loop quantum gravity
    In this talk, I'll briefly review some possible observational consequences of loop quantum gravity. I will first address the issue of the closure of the algebra of constraints in holonomy-corrected effective loop quantum cosmology for tensor, vector, and scalar modes. I will underline some unexpected features like a possible change of signature. The associated primordial power spectrum and the basics of the related CMB analysis will be presented. The "asymptotic silence" hypothesis will be mentioned as a promising alternative. Then, I'll address the issue of the probability for inflation and the prediction of its duration from a new perspective. Finally, I'll present some prospect about the evaporation of black holes in LQG.

    Henrique de Andrade Gomes, University of California, Davis
    Shape Dynamics: a status report
    I will give an introduction to the theory of Shape Dynamics, and then comment on recent advances, obstacles and future projects.

    Dafne Guetta, ORT-Braude College & INAF-OAR
    Quantum Gravity Phenomenology with Neutrinos and high energy photons.
    I review the main properties of the Gamma Ray Bursts (GRBs) as possible sources of high energy (E>TeV) neutrinos and confirmed sources of high energy (E>GeV) photons.

    I discuss the possibility to use the data of neutrino telescopes, such as IceCube and the GeV-photon telescopes, such as Fermi’s LAT, for precision tests of Einstein's Special Relativity as applied to neutrinos and photons. My focus is on possible departures from Special Relativity that can be motivated by models of quantum space-time. I observe that neutrinos which one would not associate to a GRB, when assuming a classical spacetime picture, may well be GRB neutrinos if the possibility that Lorentz invariance is broken at very high energies is taken into account. I outline how future analyses of neutrino data should be done in order to systematically test the Lorentz Invariance Violation possibility. In addition I consider the possibility that Lorentz Invariance Violation might be responsible for the spectral lags that characterize the GeV signal observed for the remarkable GRB130427A.
    A comparison of these features for GRBs at different redshifts provides some encouragement for a redshift dependence of the effects of the type expected for a quantum-spacetime interpretation, but other aspects of the analysis appear to invite the interpretation as intrinsic properties of GRBs.

    Carlo Rovelli, Le Centre de Physique Théorique
    What have we learned so far about quantum gravity?
    I try to make the point about what we know and what we do not yet know about the possibility of writing a quantum theory of gravity.

    Frank Saueressig, Radboud University Nijmegen
    Black holes in Asymptotically Safe Gravity
    In this talk, I will briefly review the main ingredients of the gravitational asymptotic safety program before focusing on the phenomenological consequences originating from the scale-dependent couplings characteristic for the theory. In particular, I will discuss recent unexpected developments in unveiling the structure of microscopic black holes within Asymptotic Safety: in the asymptotic UV the structure of the quantum solutions is universal and given by the classical Schwarzschild-de Sitter solution, entailing a self-similarity between the classical and quantum regime. As a consequence asymptotically safe black holes evaporate completely and no Planck-size remnants are formed. The relation of these results to previous criticism that Asymptotic Safety does not reproduce the state-count of a conformal field theory will be addressed.

    David Skinner, DAMTP & Institute for Advanced Study
    Twistor Strings for N=8 Supergravity
    The perturbative S-matrix of General Relativity has a rich and fascinating geometric structure that is completely obscured by its traditional description in terms of Feynman diagrams. I'll explain a new way of looking at four dimensional supergravity: as a string theory in twistor space. All tree-level amplitudes in the theory can be described by algebraic curves in Penrose's nonlinear graviton.

    Madhavan Varadarajan, Raman Research Institute
    Towards a Consistent Quantum Dynamics for Euclidean LQG: a weak coupling limit
    Spacetime covariance in canonical quantum gravity is tied to the existence of an anomaly free representation of its constraint algebra. I will argue that establishing the existence of such a representation in the LQG context requires the consideration of higher than unit density weight Hamiltonian constraints. Smolin's weak coupling limit of Euclidean gravity, while simpler than full blown gravity , still exhibits an open constraint algebra isomorphic to that of gravity and offers an ideal testing ground for the investigation of the quantum constraint algebra of such higher density constraints. I will report on recent progress on this issue in the context of an LQG type quantization of this system. Certain features of the constructions such as the encoding of the action of the quantum constraint in terms of operator valued diffeomorphisms may play a key role in the definition of a consistent quantum dynamics for LQG.
     
  4. Jul 5, 2013 #3

    marcus

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    The list of parallel session talks hasn't been posted yet AFAIK. Another longtime PF member will be giving a talk in parallel session on Friday, and there may be others I just don't happen to be aware of. Here's the posted list of plenary speakers:

    Ivan Agullo, DAMTP Cambridge
    Abhay Ashtekar, Pennsylvania State University
    Aurelien Barrau, Universite Joseph Fourier
    Eugenio Bianchi, Perimeter Institute
    Steve Carlip, University of California, Davis
    Fay Dowker, Imperial College, London
    Henrique de Andrade Gomes, University of California, Davis
    Dafne Guetta, ORT-Braude College & INAF-OAR
    Razvan Gurau, Université Paris-Sud
    Frank Hellmann, Max Planck Institute for Gravitational Physics
    Viqar Husain, University of New Brunswick
    Kirill Krasnov, University of Nottingham
    Etera Livine, Ens de Lyon
    Renate Loll, Radboud University Nijmegen
    Alejandro Perez, Centre de Physique Theorique
    Vincent Rivasseau, Universite Paris-Sud XI Orsay
    Carlo Rovelli, Le Centre de Physique Théorique
    Frank Saueressig, Radboud University Nijmegen
    David Skinner, DAMTP Cambridge, Institute for Advanced Study
    Bill Unruh, University of British Columbia
    Madhavan Varadarajan, Raman Research Institute
     
  5. Jul 9, 2013 #4

    marcus

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    Here's a partial schedule of the talks. The MTTF afternoons are split into three parallel sessions with 20 minute talks grouped by theme: Phenomenology, QuantumCosmology, Black Holes, Canonical QG, Spinfoams, ShapeDynamics, Group Field Theory&Tensor Models, Quantum Foundations, Discrete Approaches, Renormalization...
    Wednesday afternoon is a holiday.
    The morning sessions MTWTF have 45 minute plenary talks, usually 4 of them. Titles and abstracts for about half the morning talks have been posted.
    http://www.perimeterinstitute.ca/conferences/loops-13
    =============
    Monday, July 22, 2013
    9:00-9:10am Welcome and Opening Remarks
    9:10-9:55am Ivan Agullo A Quantum Gravity Extension of the Inflationary Scenario
    9:55-10:40am Aurelien Barrau Some Possible Ways to Observe Consequences of Loop Quantum Gravity
    11:00-11:45am Dafne Guetta Quantum Gravity Phenomenology with Neutrinos and High Energy Photons
    11:45-12:30pm Henrique de Andrade Gomes Shape Dynamics: a Status Report

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: M. Bojowald, S. Gielen, E. Alesci, J. Engle
    Shape Dynamics: J. Barbour, F. Mercati, T. Koslowski, K. Thebault, M. Lostaglio
    Spin Foams Mixed: A. Riello, S. Steinhaus, W. Kaminski, M. Han, G. Immirzi
    Black Holes: L. Freidel, A. Coutant, A. Lee, C. Coleman-Smith

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: E. Wilson-Ewing, J. Grain, L. Linsefors
    Shape Dynamics: S. Gryb, D. Wise, V. Shyam, J. Hazbourn
    Spin Foams Mixed: S. Speziale , J. Hnybida, W. Weiland, A. Mikovic
    Black Holes: J. Pullin, M. Smerlak, Y. Yokokura, K. Lochan
    ========================
    Tuesday, July 23, 2013
    9:00-9:45am Alejandro Perez, TBA
    9:45-10:30am Eugenio Bianchi, TBA
    11:00-11:45am Bill Unruh, TBA
    11:45-12:30pm Frank Saueressig Black Holes in Asymptotically Safe Gravity

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Renormalization: D. Benedetti, T. Morris, A. Codello, A. Rodigast
    Phenomenology: J. Granot, J. Bolmont, G. Palmisano, G. Gubitosi, L. Chen
    Canonical Quantum Gravity: J. Lewandowski, M. Kagan, M. Assanioussi, J. Swiezewski
    Black Holes: D. Pranzetti, H. Haggard, Y. Neiman N. Bodendorfer, M. Geiller

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Renormalizaition: M. Martin-Benito, S. Carrozza, J. Cooperman
    Phenomenology:A. Banburski, T. Rempel, N. Loret, B. Schroers, P. Osei
    Canonical Quantum Gravity: M. Dupuis, G. Sellaroli, J. Ziprick, M. Venkatesh
    Quantum Cosmology: M. Johnson, M. Kramer, A. Dapor, G. Mena Marugan

    6:20-7:30pm
    Panel Discussion
    ==============
    Wednesday, July 24, 2013
    9:00-9:45am Etera Livine, TBA
    9:45-10:30 David Skinner, Twistor Strings for N=8 Supergravity
    11:00-11:45am Razvan Gurau, TBA
    11:45-12:30pm Vincent Rivasseau, TBA
    12:30-12:40pm Special Announcement
    12:40-1:00pm Conference Photo
    ==================
    Thursday, July 25, 2013
    9:00-9:45am Frank Hellmann, TBA
    9:45-10:30am Fay Dowker, TBA
    11:00-11:45am Steve Carlip, TBA
    11:45-12:30pm Renate Loll, TBA

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Group Field Theory, Tensor Models: V. Bonzom, D. Oriti, J. Ryan, M. Raasakka, T. Krajewski
    Phenomenology: I. Fuentes, A. Marciano, S. Alexander, A. Eichhorn, D. Minic
    Canonical Quantum Gravity: C. Tomlin, S. Brahma, A. Stottmeister, J. Olmedo, R. Gambini
    Discrete Approaches: P. Hoehn, J. Miller, A. Trout, L. Glaser

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Group Field Theory, Tensor Models: D. Ousmane Samary, L. Sindoni, S. Dartois, J. Ben Geloun
    Phenomenology: H. Westman, A. Ballesteros, S. Bianco, G. Amelino-Camelia
    Canonical Quantum Gravity: S. Lanery, M. Hanusch, M. Campiglia, Y. Ma
    Discrete Approaches: S. Surya, J. Zapata, A. Garcia-Chung, G. Date
    =================
    Friday, July 26, 2013
    9:00-9:45am Madhavan Varadarajan Towards a Consistent Quantum Dynamics for Euclidean LQG: A Weak Coupling Limit
    9:45-10:30am Kirill Krasnov, TBA
    11:00-11:45am Viqar Husain, TBA
    11:45-12:45pm Abhay Ashtekar, Carlo Rovelli,
    Promising Paths: What Have We Learned So Far About Quantum Gravity?
    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology:T. Cailleteau, D. Martin de Blas, E. Martin-Martinez, S. Seahra, A. Contillo
    Quantum Foundations: R. Oeckl, M. Mueller, R. Spekkens, J. Oppenheim, L. Smolin
    Discrete Approaches / Mixed Session: B. Dittrich, G. Chirco, E. Kur, C. Duston, J. Thurigen
    Canonical Quantum Gravity / Spin Foams Mixed: A. Zipfel, A. Baratin, M. Zhang, A. Chaharsough Shirazi, F. Anza

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: F. Vidotto, H. Hernandez, E. Montoya, M. Hogan,
    Quantum Foundations: D. Schroeren, A. Doering, P. Bertozzini, B. Hartmann
    Renormalization: M. Anber, T. Henz, K. Falls
    Mixed Session: M. Reisenberger, J. Diaz-Polo, V. Astuti, S. Major
    6:00pm Wrap Up and Final Remarks
     
    Last edited: Jul 9, 2013
  6. Jul 9, 2013 #5

    marcus

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    There are 8 afternoon periods, each running 4 parallel sessions, for a total of 32. to get a rough indicator of the amount of activity in the various areas I counted how many of the 32 sessions were devoted to each:
    QuantumCosmology (5)
    Canonical QG (4 and 1/2)
    Phenomenology (4)
    BlackHoles (3)
    Renormalization (3)
    Spinfoams (2 and 1/2)
    Discrete Approaches (2 and 1/2)
    ShapeDynamics (2)
    GFT&Tensor (2)
    Quantum Foundations (2)
    Misc. (1 and 1/2)

    It's not clear what a count like this means, if anything. Perhaps there's some indication of where the most activity is, and in which directions the researcher's interests are tending---plus also this could indicate what the organizers themselves think are important directions of research and/or ones the participants will want to hear about.

    To me, it seems significant that 5 sessions out of the 32 are devoted to Quantum Cosmology, and 4 out of the 32 to Phenomenology. I was already inclined to think of QC and Pheno as basic driving lines of investigation that generate interest in Loop-and-allied qg and which ultimately guide its development. The Early Universe (which we now see with advanced instruments) is a nexus of puzzles and observations that need to be explained, and can only be explained through a theory of quantum gravity.

    But others (such as Tom Stoer) have often pointed out the importance of completing the Canonical version of LQG. And one notices that almost as many (4 and 1/2) sessions are devoted to Canonical QG as to to Cosmology.
     
    Last edited: Jul 9, 2013
  7. Jul 11, 2013 #6

    marcus

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    Updated list of abstracts of plenary talks:
    Ivan Agullo, DAMTP Cambridge
    A Quantum Gravity Extension of the Inflationary Scenario
    Since the standard inflationary paradigm is based on quantum field theory on classical space-times, it excludes the Planck era. Using techniques from loop quantum gravity, the theory is extended to overcome this limitations. The new framework sharpens conceptual issues by distinguishing between the true and apparent trans-Planckian difficulties and provides sufficient conditions under which the true difficulties can be overcome within a quantum gravity theory, with interesting lessons for both theory and observations.

    Abhay Ashtekar, Pennsylvania State University
    Promising Paths
    In LQG we work in the spirit of Antonio Machado: "Traveler, there is no path; Paths are made by walking." I will present a bird's eye view of some of the paths that have emerged since Loops 11 and offer a few suggestions.

    Aurelien Barrau, Universite Joseph Fourier
    Some possible ways to observe consequences of loop quantum gravity
    In this talk, I'll briefly review some possible observational consequences of loop quantum gravity. I will first address the issue of the closure of the algebra of constraints in holonomy-corrected effective loop quantum cosmology for tensor, vector, and scalar modes. I will underline some unexpected features like a possible change of signature. The associated primordial power spectrum and the basics of the related CMB analysis will be presented. The "asymptotic silence" hypothesis will be mentioned as a promising alternative. Then, I'll address the issue of the probability for inflation and the prediction of its duration from a new perspective. Finally, I'll present some prospect about the evaporation of black holes in LQG.

    Steve Carlip, University of California, Davis
    Spontaneous Dimensional Reduction?
    Several lines of evidence hint that quantum gravity at distances a bit larger than the Planck scale may become effectively two-dimensional. I will summarize the evidence for this "spontaneous dimensional reduction," and suggest a further argument based on the effect of vacuum fluctuations on light cones. If this description proves to be correct, it suggests an interesting relationship between small-scale quantum spacetime and the behavior of cosmologies near a spacelike singularity.

    Fay Dowker, Imperial College, London
    Causal Sets and the Quantum of Action
    The struggle between local and global concepts in physics comes to a head in causal set quantum gravity. Local physics -- and general relativity in particular -- must be recovered in a continuum approximation if the theory is to be successful but causal sets are inherently non-local entities. I will describe a family of causal set actions labelled by dimension, each of which is nonlocal and yet, when applied to certain causal sets, approximates the Einstein Hilbert action and is therefore effectively local. I will explain why this is a source of hope that causal set theory has a continuum approximation.

    Henrique de Andrade Gomes, University of California, Davis
    Shape Dynamics: a status report
    I will give an introduction to the theory of Shape Dynamics, and then comment on recent advances, obstacles and future projects.

    Dafne Guetta, ORT-Braude College & INAF-OAR
    Quantum Gravity Phenomenology with Neutrinos and high energy photons.
    I review the main properties of the Gamma Ray Bursts (GRBs) as possible sources of high energy (E>TeV) neutrinos and confirmed sources of high energy (E>GeV) photons.
    I discuss the possibility to use the data of neutrino telescopes, such as IceCube and the GeV-photon telescopes, such as Fermi’s LAT, for precision tests of Einstein's Special Relativity as applied to neutrinos and photons. My focus is on possible departures from Special Relativity that can be motivated by models of quantum space-time. I observe that neutrinos which one would not associate to a GRB, when assuming a classical spacetime picture, may well be GRB neutrinos if the possibility that Lorentz invariance is broken at very high energies is taken into account. I outline how future analyses of neutrino data should be done in order to systematically test the Lorentz Invariance Violation possibility. In addition I consider the possibility that Lorentz Invariance Violation might be responsible for the spectral lags that characterize the GeV signal observed for the remarkable GRB130427A.
    A comparison of these features for GRBs at different redshifts provides some encouragement for a redshift dependence of the effects of the type expected for a quantum-spacetime interpretation, but other aspects of the analysis appear to invite the interpretation as intrinsic properties of GRBs.

    Razvan Gurau, Universite Paris-Sud
    The non perturbative 1/N expansion of Tensor Models
    I will present the recently obtained non perturbative 1/N expansion of tensor models. The correlation functions are shown to be analytic in the coupling constant in some domain of the complex plane and to support appropriate scaling bounds at large N. Surprisingly, the non perturbative setting turns out to be a powerful computational tool allowing the explicit evaluation order by order (with bounded rest terms) of the correlations.

    Kirill Krasnov, University of Notthingham
    Diffeomorphism Invariant Gauge Theories
    I will describe a very large class of gauge theories that do not use any external structure such as e.g. a spacetime metric in their construction. When the gauge group is taken to be SL(2) these theories describe interacting gravitons, with GR being just a particular member of a whole family of gravity theories. Taking larger gauge groups one obtains gravity coupled to various matter systems. In particular, I will show how gravity together with Yang-Mills gauge fields arise from one and the same diffeomorphism invariant gauge theory Lagrangian. Finally, I will describe what is known about these theories quantum mechanically.

    Etera Livine, Ens de Lyon
    Spinor and Twistor networks in Loop Gravity
    I will review the reformulation of the loop gravity phase space in terms of spinor networks and twistor networks, and present how these techniques can be used to write spinfoam amplitudes as discretized path integrals and to study the dynamics that they define (recursion, Hamiltonian constraints as differential equations).

    Alejandro Perez, Centre de Physique Theorique
    Black holes in loop quantum gravity: new insights and perspectives from semiclassical consistency
    I will argue that the recently introduced quasilocal framework for black hole mechanics (based on the form of the near horizon geometry of stationary black holes (BHs)) together with an additional assumption on the degeneracy of the area spectrum in quantum gravity (holography for non geometric degrees of freedom) leads to agreement between the statistical mechanical treatment of quantum black holes and standard semiclassical results in BH thermodynamics. More precisely, up to small quantum corrections, quantum black holes satisfy the following properties:
    Equilibrium is attain at Hawking temperature, entropy is Bekenstein-Hawking entropy, and fluctuations of the horizon area are small.
    Moreover, under the above assumption, an explicit correspondence between the statistical mechanical treatment of the fundamental LQG degrees of freedom and the semiclassical Euclidean path integral formulation can be explicitly established.

    Carlo Rovelli, Le Centre de Physique Théorique
    What have we learned so far about quantum gravity?
    I try to make the point about what we know and what we do not yet know about the possibility of writing a quantum theory of gravity.

    Frank Saueressig, Radboud University Nijmegen
    Black holes in Asymptotically Safe Gravity
    In this talk, I will briefly review the main ingredients of the gravitational asymptotic safety program before focusing on the phenomenological consequences originating from the scale-dependent couplings characteristic for the theory. In particular, I will discuss recent unexpected developments in unveiling the structure of microscopic black holes within Asymptotic Safety: in the asymptotic UV the structure of the quantum solutions is universal and given by the classical Schwarzschild-de Sitter solution, entailing a self-similarity between the classical and quantum regime. As a consequence asymptotically safe black holes evaporate completely and no Planck-size remnants are formed. The relation of these results to previous criticism that Asymptotic Safety does not reproduce the state-count of a conformal field theory will be addressed.

    David Skinner, DAMTP & Institute for Advanced Study
    Twistor Strings for N=8 Supergravity
    The perturbative S-matrix of General Relativity has a rich and fascinating geometric structure that is completely obscured by its traditional description in terms of Feynman diagrams. I'll explain a new way of looking at four dimensional supergravity: as a string theory in twistor space. All tree-level amplitudes in the theory can be described by algebraic curves in Penrose's nonlinear graviton

    Madhavan Varadarajan, Raman Research Institute
    Towards a Consistent Quantum Dynamics for Euclidean LQG: a weak coupling limit
    Spacetime covariance in canonical quantum gravity is tied to the existence of an anomaly free representation of its constraint algebra. I will argue that establishing the existence of such a representation in the LQG context requires the consideration of higher than unit density weight Hamiltonian constraints. Smolin's weak coupling limit of Euclidean gravity, while simpler than full blown gravity , still exhibits an open constraint algebra isomorphic to that of gravity and offers an ideal testing ground for the investigation of the quantum constraint algebra of such higher density constraints. I will report on recent progress on this issue in the context of an LQG type quantization of this system. Certain features of the constructions such as the encoding of the action of the quantum constraint in terms of operator valued diffeomorphisms may play a key role in the definition of a consistent quantum dynamics for LQG.

    ==========

    The morning sessions MTWTF usually have four 45 minute plenary talks. The MTTF afternoons are split into three parallel sessions grouped by theme with talks 20 minute unless indicated. Speakers giving longer review talks in the afternoon parallel sessions are highlighted.
    http://www.perimeterinstitute.ca/conferences/loops-13
    =============
    Monday, July 22, 2013
    9:00-9:10am Welcome and Opening Remarks
    9:10-9:55am Ivan Agullo A Quantum Gravity Extension of the Inflationary Scenario
    9:55-10:40am Aurelien Barrau Some Possible Ways to Observe Consequences of Loop Quantum Gravity
    11:00-11:45am Dafne Guetta Quantum Gravity Phenomenology with Neutrinos and High Energy Photons
    11:45-12:30pm Henrique de Andrade Gomes Shape Dynamics: a Status Report

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: M. Bojowald, S. Gielen, E. Alesci, J. Engle
    Shape Dynamics: J. Barbour, F. Mercati, T. Koslowski, K. Thebault, M. Lostaglio
    Spin Foams Mixed: A. Riello, S. Steinhaus, W. Kaminski, M. Han, G. Immirzi
    Black Holes: L. Freidel, A. Coutant, A. Lee, C. Coleman-Smith

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: E. Wilson-Ewing, J. Grain, L. Linsefors
    Shape Dynamics: S. Gryb, D. Wise, V. Shyam, J. Hazbourn
    Spin Foams Mixed: S. Speziale , J. Hnybida, W. Weiland, A. Mikovic
    Black Holes: J. Pullin, M. Smerlak, Y. Yokokura, K. Lochan
    ========================
    Tuesday, July 23, 2013
    9:00-9:45am Alejandro Perez Black holes in loop quantum gravity: new insights and perspectives from semiclassical consistency
    9:45-10:30am Eugenio Bianchi, TBA
    11:00-11:45am Bill Unruh, TBA
    11:45-12:30pm Frank Saueressig Black Holes in Asymptotically Safe Gravity

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Renormalization: D. Benedetti, T. Morris, A. Codello, A. Rodigast
    Phenomenology: J. Granot, J. Bolmont, G. Palmisano, G. Gubitosi, L. Chen
    Canonical Quantum Gravity: J. Lewandowski, M. Kagan, M. Assanioussi, J. Swiezewski
    Black Holes: D. Pranzetti, H. Haggard, Y. Neiman N. Bodendorfer, M. Geiller

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Renormalizaition: M. Martin-Benito, S. Carrozza, J. Cooperman
    Phenomenology:A. Banburski, T. Rempel, N. Loret, B. Schroers, P. Osei
    Canonical Quantum Gravity: M. Dupuis, G. Sellaroli, J. Ziprick, M. Venkatesh
    Quantum Cosmology: M. Johnson, M. Kramer, A. Dapor, G. Mena Marugan

    6:20-7:30pm
    Panel Discussion
    ==============
    Wednesday, July 24, 2013
    9:00-9:45am Etera Livine Spinor and Twistor networks in Loop Gravity
    9:45-10:30 David Skinner, Twistor Strings for N=8 Supergravity
    11:00-11:45am Razvan Gurau The non perturbative 1/N expansion of Tensor Models
    11:45-12:30pm Vincent Rivasseau, TBA
    12:30-12:40pm Special Announcement
    12:40-1:00pm Conference Photo
    ==================
    Thursday, July 25, 2013
    9:00-9:45am Frank Hellmann, TBA
    9:45-10:30am Fay Dowker Causal Sets and the Quantum of Action
    11:00-11:45am Steve Carlip Spontaneous Dimensional Reduction?
    11:45-12:30pm Renate Loll, TBA

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Group Field Theory, Tensor Models: V. Bonzom, D. Oriti, J. Ryan, M. Raasakka, T. Krajewski
    Phenomenology: I. Fuentes, A. Marciano, S. Alexander, A. Eichhorn, D. Minic
    Canonical Quantum Gravity: C. Tomlin, S. Brahma, A. Stottmeister, J. Olmedo, R. Gambini
    Discrete Approaches: P. Hoehn, J. Miller, A. Trout, L. Glaser

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Group Field Theory, Tensor Models: D. Ousmane Samary, L. Sindoni, S. Dartois, J. Ben Geloun
    Phenomenology: H. Westman, A. Ballesteros, S. Bianco, G. Amelino-Camelia
    Canonical Quantum Gravity: S. Lanery, M. Hanusch, M. Campiglia, Y. Ma
    Discrete Approaches: S. Surya, J. Zapata, A. Garcia-Chung, G. Date
    =================
    Friday, July 26, 2013
    9:00-9:45am Madhavan Varadarajan Towards a Consistent Quantum Dynamics for Euclidean LQG: A Weak Coupling Limit
    9:45-10:30am Kirill Krasnov Diffeomorphism Invariant Gauge Theories
    11:00-11:45am Viqar Husain, TBA
    11:45-12:45pm Abhay Ashtekar, Carlo Rovelli,
    Promising Paths: What Have We Learned So Far About Quantum Gravity?
    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology:T. Cailleteau, D. Martin de Blas, E. Martin-Martinez, S. Seahra, A. Contillo
    Quantum Foundations: R. Oeckl, M. Mueller, R. Spekkens, J. Oppenheim, L. Smolin
    Discrete Approaches / Mixed Session: B. Dittrich, G. Chirco, E. Kur, C. Duston, J. Thurigen
    Canonical Quantum Gravity / Spin Foams Mixed: A. Zipfel, A. Baratin, M. Zhang, A. Chaharsough Shirazi, F. Anza

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: F. Vidotto, H. Hernandez, E. Montoya, M. Hogan,
    Quantum Foundations: D. Schroeren, A. Doering, P. Bertozzini, B. Hartmann
    Renormalization: M. Anber, T. Henz, K. Falls
    Mixed Session: M. Reisenberger, J. Diaz-Polo, V. Astuti, S. Major
    6:00pm Wrap Up and Final Remarks
     
    Last edited: Jul 11, 2013
  8. Jul 12, 2013 #7

    marcus

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    Two more abstracts for plenary talks (Wednesday and Friday) were posted today:

    Viqar Husain, University of New Brunswick
    Scenes from polymer quantization
    A regime of "polymer quantum field theory on curved spacetime" should emerge in a low energy approximation of quantum gravity based on LQG ideas. This era should be characterized by a polymer scale, and give modifications to the usual semiclassical approximation. I will describe work on gravitational collapse, cosmology, and statistical mechanics in this setting. Results include models of horizon evaporation, inflation and graceful exit without an inflaton potential, and an indication of dimensional reduction from 4 to 2.5 dimensions.

    Vincent Rivasseau, Universite Paris-Sud XI Orsay
    The Tensor Track
    I will present the tensorial renormalization group approach to quantum gravity and the tentative scenario it suggests for the emergence of space-time.
    ================
    recent publications from other speakers, for reference:
    http://arxiv.org/abs/1307.1420
    Approximation methods in Loop Quantum Cosmology: From Gowdy cosmologies to inhomogeneous models in Friedmann-Robertson-Walker geometries
    Mercedes Martín-Benito, Daniel Martín-de Blas, Guillermo A. Mena Marugán
    (see Tuesday 4:40pm)
    http://arxiv.org/abs/1307.1679
    Holonomy spin foam models: Asymptotic geometry of the partition function
    Frank Hellmann, Wojciech Kaminski
    (see Thursday 9:00am)
     
    Last edited: Jul 12, 2013
  9. Jul 12, 2013 #8

    marcus

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    Viqar Husain's talk sounds kind of interesting so I fetched the publications that it seems likely to be based on:
    http://arxiv.org/abs/1207.6714
    Primordial polymer perturbations
    Sanjeev S. Seahra (New Brunswick U., Dept. Math. Stat.), Iain A. Brown (Inst. Theor. Astrophys., Oslo), Golam Mortuza Hossain (IISER, Kolkata), Viqar Husain (New Brunswick U., Dept. Math. Stat.).
    (Submitted on 28 Jul 2012)
    18 pages, 10 figures. Published in JCAP 1210 (2012) 041
    We study the generation of primordial fluctuations in pure de Sitter inflation where the quantum scalar field dynamics are governed by polymer (not Schrödinger) quantization. This quantization scheme is related to, but distinct from, the structures employed in Loop Quantum Gravity; and it modifies standard results above a polymer energy scale M*. We recover the scale invariant Harrison Zel’dovich spectrum for modes that have wavelengths bigger than M*-1 at the start of inflation.
    The primordial spectrum for modes with initial wavelengths smaller than M*-1 exhibits oscillations superimposed on the standard result. The amplitude of these oscillations is proportional to the ratio of the inflationary Hubble parameter H to the polymer energy scale. For reasonable choices of M*, we find that polymer effects are likely unobservable in CMB angular power spectra due to cosmic variance uncertainty, but future probes of baryon acoustic oscillations may be able to directly constrain the ratio H/M*.

    http://arxiv.org/abs/arXiv:1305.2814
    High energy modifications of blackbody radiation and dimensional reduction
    Viqar Husain, Sanjeev S. Seahra, Eric J. Webster
    (Submitted on 13 May 2013)
    Quantization prescriptions that realize generalized uncertainty relations (GUP) are motivated by quantum gravity arguments that incorporate a fundamental length scale. We apply two such methods, polymer and deformed Heisenberg quantization, to scalar field theory in Fourier space. These alternative quantizations modify the oscillator spectrum for each mode, which in turn affects the blackbody distribution. We find that for a large class of modifications, the equation of state relating pressure P and energy density ρ interpolates between P=ρ/3 at low T and P=2ρ/3 at high T, where T is the temperature. Furthermore, the Stefan-Boltzman law gets modified from ρ~T4 to ρ~T5/2 at high temperature. This suggests an effective reduction to 2.5 spacetime dimensions at high energy.
    11 pages, 6 figures

    Viqar Husain's talk is in plenary session at 11AM on Friday.
     
    Last edited: Jul 12, 2013
  10. Jul 15, 2013 #9

    marcus

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    Updated list of abstracts of plenary talks:
    Ivan Agullo, DAMTP Cambridge
    A Quantum Gravity Extension of the Inflationary Scenario
    Since the standard inflationary paradigm is based on quantum field theory on classical space-times, it excludes the Planck era. Using techniques from loop quantum gravity, the theory is extended to overcome this limitations. The new framework sharpens conceptual issues by distinguishing between the true and apparent trans-Planckian difficulties and provides sufficient conditions under which the true difficulties can be overcome within a quantum gravity theory, with interesting lessons for both theory and observations.

    Abhay Ashtekar, Pennsylvania State University
    Promising Paths
    In LQG we work in the spirit of Antonio Machado: "Traveler, there is no path; Paths are made by walking." I will present a bird's eye view of some of the paths that have emerged since Loops 11 and offer a few suggestions.

    Aurelien Barrau, Universite Joseph Fourier
    Some possible ways to observe consequences of loop quantum gravity
    In this talk, I'll briefly review some possible observational consequences of loop quantum gravity. I will first address the issue of the closure of the algebra of constraints in holonomy-corrected effective loop quantum cosmology for tensor, vector, and scalar modes. I will underline some unexpected features like a possible change of signature. The associated primordial power spectrum and the basics of the related CMB analysis will be presented. The "asymptotic silence" hypothesis will be mentioned as a promising alternative. Then, I'll address the issue of the probability for inflation and the prediction of its duration from a new perspective. Finally, I'll present some prospect about the evaporation of black holes in LQG.

    Eugenio Bianchi, Perimeter Institute
    Entanglement, Bekenstein-Hawking Entropy, and Spinfoams
    I review recent developments on vacuum entanglement perturbations in perturbative quantum gravity and spinfoams, and discuss their relevance for understanding the nature of black hole entropy.

    Steve Carlip, University of California, Davis
    Spontaneous Dimensional Reduction?
    Several lines of evidence hint that quantum gravity at distances a bit larger than the Planck scale may become effectively two-dimensional. I will summarize the evidence for this "spontaneous dimensional reduction," and suggest a further argument based on the effect of vacuum fluctuations on light cones. If this description proves to be correct, it suggests an interesting relationship between small-scale quantum spacetime and the behavior of cosmologies near a spacelike singularity.

    Fay Dowker, Imperial College, London
    Causal Sets and the Quantum of Action
    The struggle between local and global concepts in physics comes to a head in causal set quantum gravity. Local physics -- and general relativity in particular -- must be recovered in a continuum approximation if the theory is to be successful but causal sets are inherently non-local entities. I will describe a family of causal set actions labelled by dimension, each of which is nonlocal and yet, when applied to certain causal sets, approximates the Einstein Hilbert action and is therefore effectively local. I will explain why this is a source of hope that causal set theory has a continuum approximation.

    Henrique de Andrade Gomes, University of California, Davis
    Shape Dynamics: a status report
    I will give an introduction to the theory of Shape Dynamics, and then comment on recent advances, obstacles and future projects.

    Dafne Guetta, ORT-Braude College & INAF-OAR
    Quantum Gravity Phenomenology with Neutrinos and high energy photons.
    I review the main properties of the Gamma Ray Bursts (GRBs) as possible sources of high energy (E>TeV) neutrinos and confirmed sources of high energy (E>GeV) photons.
    I discuss the possibility to use the data of neutrino telescopes, such as IceCube and the GeV-photon telescopes, such as Fermi’s LAT, for precision tests of Einstein's Special Relativity as applied to neutrinos and photons. My focus is on possible departures from Special Relativity that can be motivated by models of quantum space-time. I observe that neutrinos which one would not associate to a GRB, when assuming a classical spacetime picture, may well be GRB neutrinos if the possibility that Lorentz invariance is broken at very high energies is taken into account. I outline how future analyses of neutrino data should be done in order to systematically test the Lorentz Invariance Violation possibility. In addition I consider the possibility that Lorentz Invariance Violation might be responsible for the spectral lags that characterize the GeV signal observed for the remarkable GRB130427A.
    A comparison of these features for GRBs at different redshifts provides some encouragement for a redshift dependence of the effects of the type expected for a quantum-spacetime interpretation, but other aspects of the analysis appear to invite the interpretation as intrinsic properties of GRBs.

    Razvan Gurau, Universite Paris-Sud
    The non perturbative 1/N expansion of Tensor Models
    I will present the recently obtained non perturbative 1/N expansion of tensor models. The correlation functions are shown to be analytic in the coupling constant in some domain of the complex plane and to support appropriate scaling bounds at large N. Surprisingly, the non perturbative setting turns out to be a powerful computational tool allowing the explicit evaluation order by order (with bounded rest terms) of the correlations.

    Frank Hellmann, Max Planck Institute for Gravitational Physics
    Asymptotic dynamics: Spin foam partition functions in the asymptotic regime
    Spin foam models are models for space time built from discrete chunks of quantized geometry. In the asymptotic regime the classical geometry is regained.
    In the last year we have seen rapid developments in our understanding of this geometry at the level of the entire partition function. In particular it was found that the geometries that contribute to the partition function in the asymptotic regime satisfy accidental curvature constraints.
    I will discuss the classic results and role of asymptotics, the recent results and their impact on the interpretation of these models.

    Viqar Husain, University of New Brunswick
    Scenes from polymer quantization
    A regime of "polymer quantum field theory on curved spacetime" should emerge in a low energy approximation of quantum gravity based on LQG ideas. This era should be characterized by a polymer scale, and give modifications to the usual semiclassical approximation. I will describe work on gravitational collapse, cosmology, and statistical mechanics in this setting. Results include models of horizon evaporation, inflation and graceful exit without an inflaton potential, and an indication of dimensional reduction from 4 to 2.5 dimensions.

    Kirill Krasnov, University of Notthingham
    Diffeomorphism Invariant Gauge Theories
    I will describe a very large class of gauge theories that do not use any external structure such as e.g. a spacetime metric in their construction. When the gauge group is taken to be SL(2) these theories describe interacting gravitons, with GR being just a particular member of a whole family of gravity theories. Taking larger gauge groups one obtains gravity coupled to various matter systems. In particular, I will show how gravity together with Yang-Mills gauge fields arise from one and the same diffeomorphism invariant gauge theory Lagrangian. Finally, I will describe what is known about these theories quantum mechanically.

    Etera Livine, Ens de Lyon
    Spinor and Twistor networks in Loop Gravity
    I will review the reformulation of the loop gravity phase space in terms of spinor networks and twistor networks, and present how these techniques can be used to write spinfoam amplitudes as discretized path integrals and to study the dynamics that they define (recursion, Hamiltonian constraints as differential equations).

    Alejandro Perez, Centre de Physique Theorique
    Black holes in loop quantum gravity: new insights and perspectives from semiclassical consistency
    I will argue that the recently introduced quasilocal framework for black hole mechanics (based on the form of the near horizon geometry of stationary black holes (BHs)) together with an additional assumption on the degeneracy of the area spectrum in quantum gravity (holography for non geometric degrees of freedom) leads to agreement between the statistical mechanical treatment of quantum black holes and standard semiclassical results in BH thermodynamics. More precisely, up to small quantum corrections, quantum black holes satisfy the following properties:
    Equilibrium is attain at Hawking temperature, entropy is Bekenstein-Hawking entropy, and fluctuations of the horizon area are small.
    Moreover, under the above assumption, an explicit correspondence between the statistical mechanical treatment of the fundamental LQG degrees of freedom and the semiclassical Euclidean path integral formulation can be explicitly established.

    Vincent Rivasseau, Universite Paris-Sud XI Orsay
    The Tensor Track
    I will present the tensorial renormalization group approach to quantum gravity and the tentative scenario it suggests for the emergence of space-time.

    Carlo Rovelli, Le Centre de Physique Théorique
    What have we learned so far about quantum gravity?
    I try to make the point about what we know and what we do not yet know about the possibility of writing a quantum theory of gravity.

    Frank Saueressig, Radboud University Nijmegen
    Black holes in Asymptotically Safe Gravity
    In this talk, I will briefly review the main ingredients of the gravitational asymptotic safety program before focusing on the phenomenological consequences originating from the scale-dependent couplings characteristic for the theory. In particular, I will discuss recent unexpected developments in unveiling the structure of microscopic black holes within Asymptotic Safety: in the asymptotic UV the structure of the quantum solutions is universal and given by the classical Schwarzschild-de Sitter solution, entailing a self-similarity between the classical and quantum regime. As a consequence asymptotically safe black holes evaporate completely and no Planck-size remnants are formed. The relation of these results to previous criticism that Asymptotic Safety does not reproduce the state-count of a conformal field theory will be addressed.

    David Skinner, DAMTP & Institute for Advanced Study
    Twistor Strings for N=8 Supergravity
    The perturbative S-matrix of General Relativity has a rich and fascinating geometric structure that is completely obscured by its traditional description in terms of Feynman diagrams. I'll explain a new way of looking at four dimensional supergravity: as a string theory in twistor space. All tree-level amplitudes in the theory can be described by algebraic curves in Penrose's nonlinear graviton

    Madhavan Varadarajan, Raman Research Institute
    Towards a Consistent Quantum Dynamics for Euclidean LQG: a weak coupling limit
    Spacetime covariance in canonical quantum gravity is tied to the existence of an anomaly free representation of its constraint algebra. I will argue that establishing the existence of such a representation in the LQG context requires the consideration of higher than unit density weight Hamiltonian constraints. Smolin's weak coupling limit of Euclidean gravity, while simpler than full blown gravity , still exhibits an open constraint algebra isomorphic to that of gravity and offers an ideal testing ground for the investigation of the quantum constraint algebra of such higher density constraints. I will report on recent progress on this issue in the context of an LQG type quantization of this system. Certain features of the constructions such as the encoding of the action of the quantum constraint in terms of operator valued diffeomorphisms may play a key role in the definition of a consistent quantum dynamics for LQG.

    ==========

    The morning sessions MTWTF usually have four 45 minute plenary talks. The MTTF afternoons are split into three parallel sessions grouped by theme with talks 20 minute unless indicated. Speakers giving longer review talks in the afternoon parallel sessions are highlighted.
    http://www.perimeterinstitute.ca/conferences/loops-13
    =============
    Monday, July 22, 2013
    9:00-9:10am Welcome and Opening Remarks
    9:10-9:55am Ivan Agullo A Quantum Gravity Extension of the Inflationary Scenario
    9:55-10:40am Aurelien Barrau Some Possible Ways to Observe Consequences of Loop Quantum Gravity
    11:00-11:45am Dafne Guetta Quantum Gravity Phenomenology with Neutrinos and High Energy Photons
    11:45-12:30pm Henrique de Andrade Gomes Shape Dynamics: a Status Report

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: M. Bojowald, S. Gielen, E. Alesci, J. Engle
    Shape Dynamics: J. Barbour, F. Mercati, T. Koslowski, K. Thebault, M. Lostaglio
    Spin Foams Mixed: A. Riello, S. Steinhaus, W. Kaminski, M. Han, G. Immirzi
    Black Holes: L. Freidel, A. Coutant, A. Lee, C. Coleman-Smith

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: E. Wilson-Ewing, J. Grain, L. Linsefors
    Shape Dynamics: S. Gryb, D. Wise, V. Shyam, J. Hazbourn
    Spin Foams Mixed: S. Speziale , J. Hnybida, W. Weiland, A. Mikovic
    Black Holes: J. Pullin, M. Smerlak, Y. Yokokura, K. Lochan
    ========================
    Tuesday, July 23, 2013
    9:00-9:45am Alejandro Perez Black holes in loop quantum gravity: new insights and perspectives from semiclassical consistency
    9:45-10:30am Eugenio Bianchi Entanglement, Bekenstein-Hawking Entropy, and Spinfoams
    11:00-11:45am Bill Unruh, TBA
    11:45-12:30pm Frank Saueressig Black Holes in Asymptotically Safe Gravity

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Renormalization: D. Benedetti, T. Morris, A. Codello, A. Rodigast
    Phenomenology: J. Granot, J. Bolmont, G. Palmisano, G. Gubitosi, L. Chen
    Canonical Quantum Gravity: J. Lewandowski, M. Kagan, M. Assanioussi, J. Swiezewski
    Black Holes: D. Pranzetti, H. Haggard, Y. Neiman N. Bodendorfer, M. Geiller

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Renormalizaition: M. Martin-Benito, S. Carrozza, J. Cooperman
    Phenomenology:A. Banburski, T. Rempel, N. Loret, B. Schroers, P. Osei
    Canonical Quantum Gravity: M. Dupuis, G. Sellaroli, J. Ziprick, M. Venkatesh
    Quantum Cosmology: M. Johnson, M. Kramer, A. Dapor, G. Mena Marugan

    6:20-7:30pm
    Panel Discussion
    ==============
    Wednesday, July 24, 2013
    9:00-9:45am Etera Livine Spinor and Twistor networks in Loop Gravity
    9:45-10:30 David Skinner, Twistor Strings for N=8 Supergravity
    11:00-11:45am Razvan Gurau The non perturbative 1/N expansion of Tensor Models
    11:45-12:30pm Vincent Rivasseau The Tensor Track
    12:30-12:40pm Special Announcement
    12:40-1:00pm Conference Photo
    ==================
    Thursday, July 25, 2013
    9:00-9:45am Frank Hellmann Asymptotic dynamics: Spin foam partition functions in the asymptotic regime
    9:45-10:30am Fay Dowker Causal Sets and the Quantum of Action
    11:00-11:45am Steve Carlip Spontaneous Dimensional Reduction?
    11:45-12:30pm Renate Loll, TBA

    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Group Field Theory, Tensor Models: V. Bonzom, D. Oriti, J. Ryan, M. Raasakka, T. Krajewski
    Phenomenology: I. Fuentes, A. Marciano, S. Alexander, A. Eichhorn, D. Minic
    Canonical Quantum Gravity: C. Tomlin, S. Brahma, A. Stottmeister, J. Olmedo, R. Gambini
    Discrete Approaches: P. Hoehn, J. Miller, A. Trout, L. Glaser

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Group Field Theory, Tensor Models: D. Ousmane Samary, L. Sindoni, S. Dartois, J. Ben Geloun
    Phenomenology: H. Westman, A. Ballesteros, S. Bianco, G. Amelino-Camelia
    Canonical Quantum Gravity: S. Lanery, M. Hanusch, M. Campiglia, Y. Ma
    Discrete Approaches: S. Surya, J. Zapata, A. Garcia-Chung, G. Date
    =================
    Friday, July 26, 2013
    9:00-9:45am Madhavan Varadarajan Towards a Consistent Quantum Dynamics for Euclidean LQG: A Weak Coupling Limit
    9:45-10:30am Kirill Krasnov Diffeomorphism Invariant Gauge Theories
    11:00-11:45am Viqar Husain Scenes from polymer quantization
    11:45-12:45pm Abhay Ashtekar, Carlo Rovelli,
    Promising Paths: What Have We Learned So Far About Quantum Gravity?
    2:30-4:10pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology:T. Cailleteau, D. Martin de Blas, E. Martin-Martinez, S. Seahra, A. Contillo
    Quantum Foundations: R. Oeckl, M. Mueller, R. Spekkens, J. Oppenheim, L. Smolin
    Discrete Approaches / Mixed Session: B. Dittrich, G. Chirco, E. Kur, C. Duston, J. Thurigen
    Canonical Quantum Gravity / Spin Foams Mixed: A. Zipfel, A. Baratin, M. Zhang, A. Chaharsough Shirazi, F. Anza

    4:40-6:00pm Parallel Discussion Groups (20 minute talks)
    Quantum Cosmology: F. Vidotto, H. Hernandez, E. Montoya, M. Hogan,
    Quantum Foundations: D. Schroeren, A. Doering, P. Bertozzini, B. Hartmann
    Renormalization: M. Anber, T. Henz, K. Falls
    Mixed Session: M. Reisenberger, J. Diaz-Polo, V. Astuti, S. Major
    6:00pm Wrap Up and Final Remarks
     
    Last edited: Jul 15, 2013
  11. Jul 16, 2013 #10

    marcus

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    Sample threading of the parallel sessions:

    M 2:20-3:10 Freidel (S-room) BH
    3:10-3:30 Kaminski (PW-room) SF
    3:30-3:50 Alesci (theater) QC
    3:50-4:10 Engle (theater) QC

    4:40-5:00 Speziale (PW-room) SF
    5:00-5:20 Hnybida (PW) SF
    5:20-5:40 Wieland (PW) SF
    5:40-6:00 Linsefors (theater)

    T 2:30-2:50 Pranzetti (S-room) BH
    2:50-3:10 Haggard (S-room) BH
    3:10-3:30 Neiman (S-room) BH
    3:30-3:50 Bodendorfer (S-room) BH
    3:50-4:10 Geiller (S-room) BH

    4:40-5:20 Martin-Benito (B-room) Renorm
    5:20-5:40 Dupuis (PW-room) CanonQG
    5:40-6:00 Cooperman (B-room) Renorm

    Th 2:30-2:50 Bonzom (B-room) GFT
    2:50-3:10 Marciano (T-room) Phenom
    3:10-3:30 Alexander (T-room) Phenom
    3:30-3:50 Eichhorn (T-room) Phenom
    3:50-4:10 Gambini (PW-room) CanonQG

    4:40-5:00 Ousmane-Samary (B-room) GFT
    5:00-5:20 Sindoni (B-room) GFT
    5:20-5:40 Bianco (T-room) Phenom
    5:40-6:00 Amelino-Camelia (T-room) Phenom

    F 2:30-2:50 Dittrich (PW-room) Discrete
    2:50-3:10 Baratin (S-room) SF
    3:10-3:30 Zhang (S-room) SF
    3:30-3:50 Oeckl (T-room) QFound
    3:50-4:10 Smolin (T-room) QFound

    4:40-5:00 Vidotto (S-room) QC
    5:00-5:20 Diaz-Polo (PW-room) cnts lim of (Voron.) graphs
    5:20-5:40 Bertozzini (T-room) 2-grp formalism
    5:40-6:00 Major (PW-room) planar g.w.
     
  12. Jul 17, 2013 #11

    marcus

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    Combined morning and afternoon schedule with sample thread though parallel sessions. For conciseness the afternoon talk titles are in condensed paraphrase.
    Monday, July 22, 2013
    9:00-9:10am Welcome and Opening Remarks
    9:10-9:55am Ivan Agullo A Quantum Gravity Extension of the Inflationary Scenario
    9:55-10:40am Aurelien Barrau Some Possible Ways to Observe Consequences of Loop Quantum Gravity
    11:00-11:45am Dafne Guetta Quantum Gravity Phenomenology with Neutrinos and High Energy Photons
    11:45-12:30pm Henrique de Andrade Gomes Shape Dynamics: a Status Report

    2:20-3:10 Freidel (S-room) BH-----non-equil. thermodynamics and space-time geometry
    3:10-3:30 Kaminski (PW-room) SF-----curvature constraints (!)
    3:30-3:50 Alesci (theater) QC-----quantum reduced Lqg (quantize first then reduce)
    3:50-4:10 Engle (theater) QC-----quantum reduced isotropy
    4:40-5:00 Speziale (PW-room) SF-----twistor Lqg introduction
    5:00-5:20 Hnybida (PW) SF-----quantum twisted geometry
    5:20-5:40 Wieland (PW) SF-----hamiltonian spinfoam
    5:40-6:00 Linsefors (theater)-----ample inflation from bounce
    ========================
    Tuesday, July 23, 2013
    9:00-9:45am Alejandro Perez Black holes in loop quantum gravity: new insights and perspectives from semiclassical consistency
    9:45-10:30am Eugenio Bianchi Entanglement, Bekenstein-Hawking Entropy, and Spinfoams
    11:00-11:45am Bill Unruh, TBA
    11:45-12:30pm Frank Saueressig Black Holes in Asymptotically Safe Gravity

    2:30-2:50 Pranzetti (S-room) BH-----evap., massive remnant
    2:50-3:10 Haggard (S-room) BH-----twisted geometry
    3:10-3:30 Neiman (S-room) BH-----imaginary part of action
    3:30-3:50 Bodendorfer (S-room) BH------entropy, imaginary immirzi
    3:50-4:10 Geiller (S-room) BH------entropy, imaginary immirzi
    4:40-5:20 Martin-Benito (B-room) Renorm-----coarsegrain spin nets and spinfoams
    5:20-5:40 Dupuis (PW-room) CanonQG-----nonzero Λ from deformed phase space
    5:40-6:00 Cooperman (B-room) Renorm-----numerical cdt, transition amplitudes

    6:20-7:30pm Discussion panel=Dittrich, Dowker, Husain, Loll, Rovelli, Saueressig (what you think are the most important things learned from QG so far) chaired by Astrid Eichhorn.
    ==============
    Wednesday, July 24, 2013
    9:00-9:45am Etera Livine Spinor and Twistor networks in Loop Gravity
    9:45-10:30 David Skinner Twistor Strings for N=8 Supergravity
    11:00-11:45am Vincent Rivasseau The Tensor Track
    11:45-12:30pm Razvan Gurau The non perturbative 1/N expansion of Tensor Models
    12:30-1:15pm Muxin Han Spinfoam Formulation of Loop Quantum Gravity
    ==================
    Thursday, July 25, 2013
    9:00-9:45am Frank Hellmann Asymptotic dynamics: Spin foam partition functions in the asymptotic regime
    9:45-10:30am Fay Dowker Causal Sets and the Quantum of Action
    11:00-11:45am Steve Carlip Spontaneous Dimensional Reduction?
    11:45-12:30pm Renate Loll, TBA

    2:30-2:50 Bonzom (B-room) GFT-----intro to tensor models and GFT
    2:50-3:10 Marciano (T-room) Phenom-----gravity explains weak chirality
    3:10-3:30 Alexander (T-room) Phenom-----gravity&weak chirality
    3:30-3:50 Eichhorn (T-room) Phenom-----diffusion probe microgeometry e.g. dimens'l reduction
    3:50-4:10 Gambini (PW-room) CanonQG-----local hamilt'n for spherical sym. QG
    4:40-5:00 Ousmane-Samary (B-room) GFT---renorm. tensor model
    5:00-5:20 Sindoni (B-room) GFT-----GFT condensates
    5:20-5:40 Bianco (T-room) Phenom-----rel. locality, causality&momentum conservation
    5:40-6:00 Amelino-Camelia (T-room) Phenom-----review of current status
    =================
    Friday, July 26, 2013
    9:00-9:45am Madhavan Varadarajan Towards a Consistent Quantum Dynamics for Euclidean LQG: A Weak Coupling Limit
    9:45-10:30am Kirill Krasnov Diffeomorphism Invariant Gauge Theories
    11:00-11:45am Viqar Husain Scenes from polymer quantization
    11:45-12:45pm Abhay Ashtekar, Carlo Rovelli,
    Promising Paths: What Have We Learned So Far About Quantum Gravity?

    2:30-2:50 Dittrich (PW-room) Discrete-----tba, (spin nets results extended to spinfoams?)
    2:50-3:10 Baratin (S-room) SF-----star product GFTs and corresp. spinfoam amplitudes.
    3:10-3:30 Zhang (S-room) SF-----null twisted geometry, spinfoam Lqg with null boundary
    3:30-3:50 Oeckl (T-room) QFound-----boundary formalism
    3:50-4:10 Smolin (T-room) QFound-----energetic causal sets (causal structure prior to geometry)
    4:40-5:00 Vidotto (S-room) QC-----twisted geometry, recovering Regge
    5:00-5:20 Diaz-Polo (PW-room)-----continuous limit of (Voron.) graphs
    5:20-5:40 Bertozzini (T-room)-----C* category formalism for relational QM
    5:40-6:00 Major (PW-room)-----planar g.w.

    6:00pm Wrap Up and Final Remarks
    ====================
    For convenience I'll bring forward the morning talk abstracts, by day:
    Monday
    Ivan Agullo, DAMTP Cambridge
    A Quantum Gravity Extension of the Inflationary Scenario
    Since the standard inflationary paradigm is based on quantum field theory on classical space-times, it excludes the Planck era. Using techniques from loop quantum gravity, the theory is extended to overcome this limitations. The new framework sharpens conceptual issues by distinguishing between the true and apparent trans-Planckian difficulties and provides sufficient conditions under which the true difficulties can be overcome within a quantum gravity theory, with interesting lessons for both theory and observations.

    Aurelien Barrau, Universite Joseph Fourier
    Some possible ways to observe consequences of loop quantum gravity
    In this talk, I'll briefly review some possible observational consequences of loop quantum gravity. I will first address the issue of the closure of the algebra of constraints in holonomy-corrected effective loop quantum cosmology for tensor, vector, and scalar modes. I will underline some unexpected features like a possible change of signature. The associated primordial power spectrum and the basics of the related CMB analysis will be presented. The "asymptotic silence" hypothesis will be mentioned as a promising alternative. Then, I'll address the issue of the probability for inflation and the prediction of its duration from a new perspective. Finally, I'll present some prospect about the evaporation of black holes in LQG.

    Dafne Guetta, ORT-Braude College & INAF-OAR
    Quantum Gravity Phenomenology with Neutrinos and high energy photons.
    I review the main properties of the Gamma Ray Bursts (GRBs) as possible sources of high energy (E>TeV) neutrinos and confirmed sources of high energy (E>GeV) photons.
    I discuss the possibility to use the data of neutrino telescopes, such as IceCube and the GeV-photon telescopes, such as Fermi’s LAT, for precision tests of Einstein's Special Relativity as applied to neutrinos and photons. My focus is on possible departures from Special Relativity that can be motivated by models of quantum space-time. I observe that neutrinos which one would not associate to a GRB, when assuming a classical spacetime picture, may well be GRB neutrinos if the possibility that Lorentz invariance is broken at very high energies is taken into account. I outline how future analyses of neutrino data should be done in order to systematically test the Lorentz Invariance Violation possibility. In addition I consider the possibility that Lorentz Invariance Violation might be responsible for the spectral lags that characterize the GeV signal observed for the remarkable GRB130427A.
    A comparison of these features for GRBs at different redshifts provides some encouragement for a redshift dependence of the effects of the type expected for a quantum-spacetime interpretation, but other aspects of the analysis appear to invite the interpretation as intrinsic properties of GRBs.

    Henrique de Andrade Gomes, University of California, Davis
    Shape Dynamics: a status report
    I will give an introduction to the theory of Shape Dynamics, and then comment on recent advances, obstacles and future projects.
    ======

    Tuesday
    Alejandro Perez, Centre de Physique Theorique
    Black holes in loop quantum gravity: new insights and perspectives from semiclassical consistency
    I will argue that the recently introduced quasilocal framework for black hole mechanics (based on the form of the near horizon geometry of stationary black holes (BHs)) together with an additional assumption on the degeneracy of the area spectrum in quantum gravity (holography for non geometric degrees of freedom) leads to agreement between the statistical mechanical treatment of quantum black holes and standard semiclassical results in BH thermodynamics. More precisely, up to small quantum corrections, quantum black holes satisfy the following properties:
    Equilibrium is attain at Hawking temperature, entropy is Bekenstein-Hawking entropy, and fluctuations of the horizon area are small.
    Moreover, under the above assumption, an explicit correspondence between the statistical mechanical treatment of the fundamental LQG degrees of freedom and the semiclassical Euclidean path integral formulation can be explicitly established.

    Eugenio Bianchi, Perimeter Institute
    Entanglement, Bekenstein-Hawking Entropy, and Spinfoams
    I review recent developments on vacuum entanglement perturbations in perturbative quantum gravity and spinfoams, and discuss their relevance for understanding the nature of black hole entropy.

    Unruh, TBA

    Frank Saueressig, Radboud University Nijmegen
    Black holes in Asymptotically Safe Gravity
    In this talk, I will briefly review the main ingredients of the gravitational asymptotic safety program before focusing on the phenomenological consequences originating from the scale-dependent couplings characteristic for the theory. In particular, I will discuss recent unexpected developments in unveiling the structure of microscopic black holes within Asymptotic Safety: in the asymptotic UV the structure of the quantum solutions is universal and given by the classical Schwarzschild-de Sitter solution, entailing a self-similarity between the classical and quantum regime. As a consequence asymptotically safe black holes evaporate completely and no Planck-size remnants are formed. The relation of these results to previous criticism that Asymptotic Safety does not reproduce the state-count of a conformal field theory will be addressed.
    ====

    Wednesday
    Etera Livine, Ens de Lyon
    Spinor and Twistor networks in Loop Gravity
    I will review the reformulation of the loop gravity phase space in terms of spinor networks and twistor networks, and present how these techniques can be used to write spinfoam amplitudes as discretized path integrals and to study the dynamics that they define (recursion, Hamiltonian constraints as differential equations).

    David Skinner, DAMTP & Institute for Advanced Study
    Twistor Strings for N=8 Supergravity
    The perturbative S-matrix of General Relativity has a rich and fascinating geometric structure that is completely obscured by its traditional description in terms of Feynman diagrams. I'll explain a new way of looking at four dimensional supergravity: as a string theory in twistor space. All tree-level amplitudes in the theory can be described by algebraic curves in Penrose's nonlinear graviton.

    Vincent Rivasseau, Universite Paris-Sud XI Orsay
    The Tensor Track
    I will present the tensorial renormalization group approach to quantum gravity and the tentative scenario it suggests for the emergence of space-time.

    Razvan Gurau, Universite Paris-Sud
    The non perturbative 1/N expansion of Tensor Models
    I will present the recently obtained non perturbative 1/N expansion of tensor models. The correlation functions are shown to be analytic in the coupling constant in some domain of the complex plane and to support appropriate scaling bounds at large N. Surprisingly, the non perturbative setting turns out to be a powerful computational tool allowing the explicit evaluation order by order (with bounded rest terms) of the correlations.

    Muxin Han, Centre de Physique
    Spinfoam Formulation of Loop Quantum Gravity
    ======

    Thursday
    Frank Hellmann, Max Planck Institute for Gravitational Physics
    Asymptotic dynamics: Spin foam partition functions in the asymptotic regime
    Spin foam models are models for space time built from discrete chunks of quantized geometry. In the asymptotic regime the classical geometry is regained.
    In the last year we have seen rapid developments in our understanding of this geometry at the level of the entire partition function. In particular it was found that the geometries that contribute to the partition function in the asymptotic regime satisfy accidental curvature constraints.
    I will discuss the classic results and role of asymptotics, the recent results and their impact on the interpretation of these models.

    Fay Dowker, Imperial College, London
    Causal Sets and the Quantum of Action
    The struggle between local and global concepts in physics comes to a head in causal set quantum gravity. Local physics -- and general relativity in particular -- must be recovered in a continuum approximation if the theory is to be successful but causal sets are inherently non-local entities. I will describe a family of causal set actions labelled by dimension, each of which is nonlocal and yet, when applied to certain causal sets, approximates the Einstein Hilbert action and is therefore effectively local. I will explain why this is a source of hope that causal set theory has a continuum approximation.

    Steve Carlip, University of California, Davis
    Spontaneous Dimensional Reduction?
    Several lines of evidence hint that quantum gravity at distances a bit larger than the Planck scale may become effectively two-dimensional. I will summarize the evidence for this "spontaneous dimensional reduction," and suggest a further argument based on the effect of vacuum fluctuations on light cones. If this description proves to be correct, it suggests an interesting relationship between small-scale quantum spacetime and the behavior of cosmologies near a spacelike singularity.

    Loll, TBA
    ======

    Friday
    Madhavan Varadarajan, Raman Research Institute
    Towards a Consistent Quantum Dynamics for Euclidean LQG: a weak coupling limit
    Spacetime covariance in canonical quantum gravity is tied to the existence of an anomaly free representation of its constraint algebra. I will argue that establishing the existence of such a representation in the LQG context requires the consideration of higher than unit density weight Hamiltonian constraints. Smolin's weak coupling limit of Euclidean gravity, while simpler than full blown gravity , still exhibits an open constraint algebra isomorphic to that of gravity and offers an ideal testing ground for the investigation of the quantum constraint algebra of such higher density constraints. I will report on recent progress on this issue in the context of an LQG type quantization of this system. Certain features of the constructions such as the encoding of the action of the quantum constraint in terms of operator valued diffeomorphisms may play a key role in the definition of a consistent quantum dynamics for LQG.

    Kirill Krasnov, University of Notthingham
    Diffeomorphism Invariant Gauge Theories
    I will describe a very large class of gauge theories that do not use any external structure such as e.g. a spacetime metric in their construction. When the gauge group is taken to be SL(2) these theories describe interacting gravitons, with GR being just a particular member of a whole family of gravity theories. Taking larger gauge groups one obtains gravity coupled to various matter systems. In particular, I will show how gravity together with Yang-Mills gauge fields arise from one and the same diffeomorphism invariant gauge theory Lagrangian. Finally, I will describe what is known about these theories quantum mechanically.

    Viqar Husain, University of New Brunswick
    Scenes from polymer quantization
    A regime of "polymer quantum field theory on curved spacetime" should emerge in a low energy approximation of quantum gravity based on LQG ideas. This era should be characterized by a polymer scale, and give modifications to the usual semiclassical approximation. I will describe work on gravitational collapse, cosmology, and statistical mechanics in this setting. Results include models of horizon evaporation, inflation and graceful exit without an inflaton potential, and an indication of dimensional reduction from 4 to 2.5 dimensions.

    Abhay Ashtekar, Pennsylvania State University
    Promising Paths
    In LQG we work in the spirit of Antonio Machado: "Traveler, there is no path; Paths are made by walking." I will present a bird's eye view of some of the paths that have emerged since Loops 11 and offer a few suggestions.

    Carlo Rovelli, Le Centre de Physique Théorique
    What have we learned so far about quantum gravity?
    I try to make the point about what we know and what we do not yet know about the possibility of writing a quantum theory of gravity.
    ========

    =================
    More information:
    http://www.perimeterinstitute.ca/conferences/loops-13
    The abstracts for the afternoon talks:
    http://www.perimeterinstitute.ca/si.../attachments/Parallel Session Abstracts_1.pdf
     
    Last edited: Jul 17, 2013
  13. Jul 25, 2013 #12

    marcus

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    Loops 2013 videos

    Here is the PIRSA list of online recorded talks.
    http://pirsa.org/C13029.
    In this catalog I think some of the most interesting talks are the 20 minute parallel session ones that are posted online in groups of 4 or so---the whole video is typically around 80 minutes.
    The ORDER of the speakers listed in catalog is not always the same as in the actual recording, so where I have watched the video, in some cases, I will list the speakers in order together with the time their segment starts. So if you want you can skip to a particular talk.
    This might save someone time if they are looking for a particular talk. Here's an example:
    http://pirsa.org/13070079
    Discrete approaches session 3
    I don't give the exact title sometimes, just rough indication what the talk is about
    Jacek Puchta (start) dipole cosmology example, calculating actual SF amplitudes, nice
    Bianca Dittrich (17:40) coarsegraining and testing quantum gravity theories ("How to solve your theory")
    Sumati Surya (37:00) causal sets, nice short introduction with recent results
    Ganashyam Date (57:30) symmetries in polymer quantization
    ============
    The idea is that if you want to get to Dittrich talk in particular this can save you time hunting for it in the total 80 minute "tape". It was listed at the end but actually came second.
    I'll try that with a few others as time permits. Maybe it's not necessary, if the listing is generally in order.
    =============
    Spinfoams session 2
    http://pirsa.org/13070045/
    Georgio Immirzi (start)--Spinors in Lorentzian spinfoams
    Jeff Hnybida (20:30)--quantum model of twisted geometry
    Wolfgang Wieland (39:00)--quantizing a truncated version of classical GR and getting EPRL amplitudes
    Aleksander Mikovic (62:00)--Spin cube models of quantum gravity (uses 2-groups, category theory)
    This turns out not to need re-listing because the regular Pirsa list is already completely adequate.
    It shows the talks in the order they occurred and they are all about the same length.
    =============
    Black holes session 3
    http://pirsa.org/13070054
    Daniele Pranzetti, Hal Haggard, Yasha Neiman, Norbert Bodendorfer, Marc Geiller
    These talks are listed in actual order too! So there does not seem much need
    Pranzetti (start)--BH entropy from KMS states of Q. Isolated Horizons (I like this a lot)
    Haggard (20:00)--General bddry field theory, thermality and entanglement (this too!)
    Neiman (41:20)--Im entropy, and EPRL (another interesting one!)
    Bodendorfer (60:00)--Wald entropy
    Geiller ( 75:00)--BI parameter, BH entropy and the reality condition
    The tape is 108 minutes, so what I'm doing seems really unnecessary. The talks really are mostly about 20 minutes so you can find what you want fairly easily.
    The main thing is just to go to http://pirsa.org/C13029
    and look down the list
     
    Last edited: Jul 25, 2013
  14. Jul 25, 2013 #13

    marcus

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    I found one where the listing needs a slight re-edit. It might interest some of us. Quite a lot of Djordje Minic's research is in string, he has some ideas of how Loop and String could combine in a single more fundamental theory. His talk was in the "phenomenology 3 session"
    The edit is simply that Stephon Alexander is listed but could not make it. Leonardo Barcaroli spoke instead. Fuentes had to be in Nottingham but gave her talk by wire. All five talks together make a 106 minutes recording.

    http://pirsa.org/13070073/
    Phenomenology session 3
    Ivette Fuentes, Antonino Marciano, Leonardo Barcaroli, Astrid Eichhorn, Djordje Minic
    Fuentes(start)--relativistic quantum technology, quantum metrology, wide audience presentation
    Marciano(27:30)--gravity explains weak chirality
    Barcaroli (50:00)--relative locality
    Eichhorn(62:00)--probing q. properties of space-time by diffusion (spectral dimension reduction...)
    Minic(84:00)--Generalized T-duality, string theory, and the real world (?...?)
     
    Last edited: Jul 26, 2013
  15. Jul 26, 2013 #14

    MTd2

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    Hey Marcus, I'd like to hear your opinion that LQC( perhaps LQG) is dead!
     
  16. Jul 26, 2013 #15

    marcus

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    Hi MTd2, good to hear from you! On that topic AFAICS Loop gravity including cosmology is at the most vital and dynamic level of activity it has ever been. I think of Etera Livine's talk as an example. It will take some time to assess what is happening in the field because one will have to have time to watch several of the 40 minute plenary talks. I will list a few and perhaps will be able to think about them over the next few days.
    http://pirsa.org/C13029
    The main thing is, this represents an amazing online resource. It will take, in some cases, repeat viewing and some time to assimilate. As a rule, the LQG plenary talks are by "new" people that you might not automatically think of if you formed an impression 5 or 10 years ago.

    There are some great non-loop talks (e.g. Renate Loll on CDT, Fay Dowker on Causets, Frank Hellmann on AsymSafe QG, Vincent Rivasseau on QG tensor style, Gomes on Shape...) but since you ask specifically about Loops I'll try to point to some plenary talks that seem representative of what's happening in Loops.

    http://pirsa.org/13070036/
    Some Possible Ways to Observe Consequences of Loop Quantum Gravity
    Aurelien Barrau (cosmology of course, this guy is amazing)
    http://pirsa.org/13070063/
    Spinor and Twistor Networks in Loop Gravity
    Etera Livine (must watch, this is an important new line of development just in past two years)
    http://pirsa.org/13070067/
    Spinfoam Formulation of Loop Quantum Gravity
    Muxin Han (significant progress here)
    http://pirsa.org/13070080/
    Towards a Consistent Quantum Dynamics for Euclidean LQG: A Weak Coupling Limit
    Madhavan Varadarajan (anomaly free representation of constraint algebra, I have to think more, didn't watch the whole talk yet)
     
    Last edited: Jul 26, 2013
  17. Jul 26, 2013 #16

    marcus

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    MTd2, when you think about it maybe the most striking thing is that when you access the Loops conference tapes you get, in the plenary talks,
    1. all these up to the minute status reports of non-loop QG fields: CDT, Shape dynamics, AsymSafe, Causets, Tensor models,...PLUS
    2. you get front-line reports on Loop developments from people whose names are not household words already: Barrau, Han, Livine, Varadarajan, Bianchi, Peres...
    That makes it a really remarkable package of information.

    That's just in the plenary talks (where each link goes to one speaker). As I have time I want to dig into the many parallel session tapes, like that Phenomenology session 3 that I was looking at a few posts back.
     
  18. Jul 26, 2013 #17

    xristy

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    also

    After which is the must watch of Skinner's talk:

    Twistor Strings for N=8 Supergravity
    http://pirsa.org/13070064/

    which has a cameo appearance of the SBT:

    http://blog.vixra.org/2013/07/19/super-yang-mills-vs-loop-quantum-gravity

    which Smolin commented on positively at the end of Skinner's talk - though Rovelli was perhaps not so taken.

    Perhaps in another thread there can be some discussion of whether and in what way it really is the SBT. Certainly the work of Cachazo, Arkani-Hamed, Skinner and others flowing out of the spinor helicity approach through twistors seems to be significant and as you indicate twistors are of some relevance in LQG these days.
     
  19. Jul 26, 2013 #18

    marcus

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    More sampling from http://pirsa.org/C13029
    The two summary talks tape is 87 minutes with the break at 37 minutes.
    http://pirsa.org/13070083

    There were some interesting non-loop-gravity talks, maybe the conference should have been called "Loops-plus" or Loops+
    Steve Carlip (spontaneous dimension reduction that happens in several QG theories may have a classical GR basis)
    http://pirsa.org/13070070/
    Kirill Krasnov (reformulating classical GR purely with the connection, no metric, no holonomy-flux algebra...)
    http://pirsa.org/13070081/
    Viqar Husain (if you apply LQG's polymer quantization to MATTER on a classical curved space-time background instead of to the geometry, there are some surprising effects, singularities are resolved, you get inflation for free etc.)
    http://pirsa.org/13070082/

    I think this Quantum Foundations session has some intriguing stuff. Total time 118 minutes. I'll identify the breaks so you can skip to whichever talk you want to watch.
    http://pirsa.org/13070084/
    Quantum Foundations - 1
    Robert Oeckl, Markus Mueller, Robert Spekkens, Jonathan Oppenheim, Lee Smolin
    Oeckl (start) only way to do general covariant QFT is using BOUNDARY of spacetime region because since there is no preferred time there is no idea of initial/final state. You don't have "states" at a particular time, you have processes occurring in a spacetime region that compat with what is observed on the boundary so you want to calculate amplitudes associated with the boundary
    Mueller (20:40) From information theoretic axioms to quantum theory and beyond (nice talk, assume properties of information and from that derive QM, vary the axioms)
    Spekkens (42:30) Causal explanation of quantum correlations (very impressive talk, you measure correlations betw things but how do you deduce what is causing what?)
    Oppenheim (70) modification of QM motivated by the BH information problem
    Smolin (95) Energetic Causal Sets and the Emergence of Spacetime (causal set is a lattice of causality arrows connecting a set of events, suppose each of those arrows was labeled with an energy and a momentum? Could you write a lagrangian in all those energy momentum labels from which space time coordinates could arise as a solution? Could you make space-time arise from a causal structure? Interesting idea. Current research with M. Cortes. An "energetic causet"is just a causet with those labels on the arrows. It is a rather minimal thing to assume for starters, surprising how much they get from it.
     
    Last edited: Jul 26, 2013
  20. Jul 27, 2013 #19

    marcus

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    More sampling from http://pirsa.org/C13029
    Quantum cosmology session 2
    http://pirsa.org/13070043
    Edward Wilson-Ewing, Julien Grain, Linda Linsefors, Andrea Dapor
    The total length is 102 minutes, with EdWE responsible for a review talk of approx. 40 minutes.
    Wilson-Ewing(start)Confronting LQC with observations
    Grain(37:30)Loop quantum cosmology in the CMB
    Linsefors(56:30)Duration of slow roll inflation as a prediction of LQC
    Dapor(77:30)QFT in quantum spacetime
    I haven't yet had time to watch enough of these talks to comment on them but will make a couple of general remarks: Linsefors' talk is based on the recent paper with Barrau which shows a new way to predict, on minimal assumptions, the extent of inflation resulting from Loop cosmology bounce
    http://arxiv.org/abs/1301.1264
    Barrau's team is on a roll, here are just a few more papers from them since the January one:
    http://arxiv.org/abs/1305.4516
    Modified Friedmann equation and survey of solutions in effective Bianchi-I loop quantum cosmology
    http://arxiv.org/abs/1307.5238
    Anomaly-free perturbations with inverse-volume and holonomy corrections in Loop Quantum Cosmology
    The other comment is that from my limited (and certainly biased) perspective the topic of Wilson-Ewing's talk is the most important one currently being addressed in the Loop gravity research community. And what he is telling in this talk is that various quantum cosmology models can be distinguished by differences in what they predict about the scalar and tensor CMB power spectrum. In this talk he discusses not only what LQC predicts but also draws comparison with several other models that resolve the singularity. Early universe observations are where the various models fight it out. :biggrin:
     
  21. Jul 29, 2013 #20

    marcus

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    Loops 2013 parallel session intervals

    My idea in this post is to show the speaker changeover times, in the recording, to make it easer to scroll to the beginning of any desired talk. This covers half the parallel sessions (the afternoons of 22 and 23 July). The first recording had 4 speakers, so I list 3 approximate times.
    If, for instance, you want to watch the talk of Antonin Coutant, you drag the time marker to around minute 42:00 of the first recording listed here.

    http://pirsa.org/13070042/
    Black Holes - 1
    Laurent Freidel, Antonin Coutant, Antony Lee, Christopher Coleman-Smith
    42:00, 60:50, 80:30

    http://pirsa.org/13070041/
    Spin Foams - 1
    Simone Speziale, Aldo Riello, Sebastian Steinhaus, Wojciech Kaminski
    38:00, 72:00, 97:00

    http://pirsa.org/13070039/
    Quantum Cosmology - 1
    Martin Bojowald, Steffen Gielen, Emanuele Alesci, Jonathan Engle
    39:00, 60:00, 83:00

    http://pirsa.org/13070040/
    Shape Dynamics - 1
    Julian Barbour, Flavio Mercati, Tim Koslowski, Karim Thebault, Matteo Giuseppe Lostaglio
    15:00, 31:00, 62:00, 84:00

    http://pirsa.org/13070043/
    Quantum Cosmology - 2
    Edward Wilson-Ewing, Julien Grain, Linda Linsefors, Andrea Dapor
    37:30, 56:30, 77:30

    http://pirsa.org/13070044/
    Shape Dynamics - 2
    Sean Gryb, Niayesh Afshordi, Vasudev Shyam, Jeffrey Hazboun
    20:00, 37:00, 57:40

    http://pirsa.org/13070045/
    Spin Foams - 2
    Giorgio Immirzi, Jeff Hnybida, Wolfgang Wieland, Aleksander Mikovic
    20:30, 39:00, 62:00

    http://pirsa.org/13070046/
    Black Holes - 2
    Jorge Pullin, Matteo Smerlak, Yuki Yokokura, Kinjalk Lochan
    16:50, 42:00, 61:30

    http://pirsa.org/13070051/
    Renormalization - 1
    Dario Benedetti, Tim Morris, Andreas Rodigast
    40:50, 79:50

    http://pirsa.org/13070052/
    Phenomenology - 1
    Jonathan Granot, Julien Bolmont, Giulia Gubitosi, Giovanni Palmisano, Linqing Chen
    21:00, 49:00, 75:00, 95:00

    http://pirsa.org/13070053/
    Canonical Quantum Gravity - 1
    Jerzy Lewandowski, Mikhail Kagan, Mehdi Assanioussi, Jedrzej Swiezewski
    43:30, 60:20. 82:00

    http://pirsa.org/13070054/
    Black Holes - 3
    Daniele Pranzetti, Hal Haggard, Yasha Neiman, Norbert Bodendorfer, Marc Geiller
    20:00, 41:20, 60:00, 75:00

    http://pirsa.org/13070055/
    Renormalization - 2
    Mercedes Martin-Benito, Sylvain Carrozza, Joshua Cooperman
    35:10, 54:40

    http://pirsa.org/13070056/
    Phenomenology - 2
    Andrzej Banburski, Trevor Rempel, Niccol Loret, Bernd Schroers, Prince Osei
    17:00, 33:20, 48:20, 72:30

    http://pirsa.org/13070057/
    Canonical Quantum Gravity - 2
    Jonathan Ziprick, Madhavan Venkatesh, Maïté Dupuis, Giuseppe Sellaroli
    22:00, 38:00, 58:30

    http://pirsa.org/13070058/
    Quantum Cosmology - 3
    Matthew Johnson, Manuel Kramer, Sanjeev Seahra, Guillermo Marugan
    22:20, 40:00, 60:30
     
    Last edited: Jul 29, 2013
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