Loops 2011: abstracts of all talks now online

[marcus]

http://loops11.iem.csic.es/loops11/index.php?option=com_content&view=article&id=75&Itemid=73

The Loops 2011 conference starts in a little over 3 weeks (23 May) in Madrid.
On the posted schedule, the titles of the talks link to abstracts. So we can see in more detail what each talk is about.

Over 160 participants. 19 plenary talks (including one on Friday by Martin B. called "How to rule out loop quantum cosmology." He is really serious about getting falsifiable )

100-or-so talks in the parallel sessions. Someone from UC Berkeley is giving a talk (on the volume operator, an important geometric observable in QG). Several people who have posted here at PF Beyond forum are giving talks. I see one giving two talks: on Monday in the Covariant/Spinfoam session and again on Friday in the Loop Cosmology session. I now see this is not unusual, several of the researchers are giving more than one presentation in the parallel sessions.

It looks like some of the most interesting talks will by by new lesser-known people.

 

[marcus]

A sampling of highlights from the 100 or so parallel session talks:


LQC Inflation and WMAP 7 Year Data.
David Sloan
Central Room. Friday, May, 27th, 15:05 - 15:25.
Abstract:
I will present a detailed analysis of the inflationary dynamics of LQC coupled to a massive scalar field using analytical and numerical methods. By combining this information with a measure on the space of solutions, I establish that the probability of a sufficiently long slow roll inflation compatible with the WMAP 7 year data is very close to 1. Several issues which occur in defining probability on a non-compact phase-space will be discussed, as will the generalization of the result to a wide class of potentials.

Observational Signatures of Loop Quantum Cosmology.
Ivan Agulló
Central Room. Friday, May, 27th, 15:25 - 15:45.
Abstract:
Inflation offers a natural mechanism to quantitatively account for the spectrum of cosmic inhomogeneities that we observe in the present universe. We show a viable scenario in which the predictions of inflation for the CMB anisotropies and galaxy distribution can be significantly modified by Loop Quantum Cosmology. The results open a promising window toward the direct observation of quantum aspects of gravity.

Observational features of Loop Quantum Cosmology.
Aurélien Barrau
Central Room. Friday, May, 27th, 15:45 - 16:05.
Abstract:
Loop Quantum Cosmology is a promising attempt to apply Loop Quantum Gravity ideas to the Universe as a whole. I will describe some possible observational features. First, I will explain how the primordial tensor power spectrum is modified, even in a de-Sitter background, through both holonomy and inverse-volume corrections. Then, I will show how the bounce leaves specific footprints on the power spectrum, in particular through the following super-inflation period. This leads to potentially relevant features in the Cosmological Microwave Background B-modes. Finally, I will present the work in progress on the construction of an anomaly-free algebra for holonomy corrected vector and scalar perturbations.

Creating Quantum Fields in Curved Spacetimes in the Lab.
Isabeau Prémont-Schwarz
Central Room. Tuesday, May, 24th, 15:45 - 16:05.
Abstract:
In this presentation we will investigate how one can create emergent curved spacetimes by locally tuning the coupling constants of condensed matter systems. In the continuum limit we thus obtain continuous effective quantum fields living on curved spacetimes. In particular, using Stingnet condensates we can obtain effective electromagnetism. We will show for example how we obtain quantum electrodynamics in a black hole (Schwarzschild) spacetime.

Effective Classical Dynamics for Loop Quantum Gravity.
Etera Livine
M. Ambientales Room. Friday, May, 27th, 15:25 - 15:45.
Abstract:
I will present the reformulation of the kinematics of loop quantum gravity in terms of spinor phase space and twisted geometry and will show how to use it to write down classical dynamics for the discrete geometry on fixed graphs. I will discuss the application of this framework to (loop quantum) cosmology.

Two by Muxin Han:
Spinfoam Fermions.
Muxin Han
M. Ambientales Room. Tuesday, May, 24th, 14:45 - 15:05.
Abstract:
We discuss fermion coupling in the framework of spinfoam quantum gravity. We analyze the gravity-fermion spinfoam model and its fermion correlation functions. We show that there is a spinfoam analog of PCT symmetry for the fermion fields on spinfoam model, where a PCT theorem is proved for spinfoam fermion correlation functions. We compute the determinant of the Dirac operator for the fermions, where two presentations of the Dirac determinant are given in terms of diagram expansions. We compute the fermion correlation functions and show that they can be given by Feynman diagrams on the spinfoams, where the Feynman propagators can be represented by a discretized path integral of a world-line action along the edges of the underlying 2-complex.

Quantum Group Spinfoam Model and its Asymptotics.
Muxin Han
M. Ambientales Room. Monday, May, 23rd, 15:25 - 15:45.
Abstract:
Recently a quantum group deformation of EPRL spinfoam model was proposed in arXiv:1012.4216 by one of the authors, and in arXiv:1012.4784 by Fairbairn and Meusburger. It is interesting to study the high spin asymptotics of the quantum group spinfoam model, to see if it gives the discrete Einstein gravity with cosmological constant as its semiclassical limit. In this article we propose a new technique, which can simplify the analysis of the high spin asymptotics for quantum group spinfoam vertex amplitude. This technique can generalize the spinfoam asymptotic analysis developed by Barrett, et al to quantum group spinfoam. As a preparation of asymptotic analysis, we define and analyze the coherent states and coherent intertwiners for quantum group, which has certain "factorization properties". We show that in the high spin limit of quantum group spinfoam, many q-deformed noncommutative ingredients become classical and commutative. In particular, the squared norm of coherent intertwiner and the (Euclidean) vertex amplitude become integrals on classical group, while there are some additional terms (written in terms of classical group variables) make quantum group corrections to the usual (classical group) coherent intertwiner and vertex amplitude. These quantum group correction terms turn out to be proportional to the deformation parameter, which hopefully gives the cosmological term as its semiclassical limit.

Holomorphic representation for spin networks and the continuum limit.
Johannes Tambornino
M. Ambientales Room. Friday, May, 27th, 15:45 - 16:05.
Abstract:
Within the holomorphic representation of spin networks spinorial variables are used to encode the kinematical information of LQG. This reformulation is gained towards a better understanding of LQG states in terms of simplicial geometries. However, so far it was unclear whether one of the main points of the whole LQG program, namely it's ability to capture the infinite number of degrees of freedom of the gravitational field by means of so called projective techniques, can be transferred to the holomorphic representation. I will analyze this question and show that it is indeed possible to construct a map that maps spin network functions onto some spinorial space in a unitary way. This map can then be used to analyze the continuum properties of LQG in the spinorial formulation.

 

[Sardano]

Are you going?

 

[marcus]

Are you going?

You know, your question makes sense! Thanks for asking. I am merely an outside observer with no connection with any research program, so normally it would not make sense for me to attend any of these conferences. But this one is so interesting I am almost thinking it was a mistake not to go! As a kind of "virtual journalistic webreporter" or some odd thing. Of course I don't mean that entirely serously. No I'm not going I have no realworld reason to go.

If you have examined the website you will have noticed an interesting thing about this conference. It welcomes rival theories.

It has been customary at these conferences to want to hear the latest developments from alternative QG and be able to ask questions and discuss so invited plenary speakers at Loops conferences have included Dijkgraaf (string), Loll (CDT), Reuter (AS), Magueijo, and many others. Also in the parallel sessions you get talks about rival developments. Apparently it is perceived as valuable and not threatening.

This year the most profound challenge and at the same time the greatest opportunity for creative innovation seems to come from SD (shape dynamics). There is an entire parallel session on the opening day (Monday 23 May) being devoted to SD.

It is actually this parallel session which makes me wish that (even though I just observe the scene and don't have any involvement) I had made arrangements to go to Madrid.

The other major new thing, I guess, is the strong showing at Loops 2011 of CMB (cosmic microwave background) phenomenology. The imminent prospect that real tests could constrain the theory. It causes excitement when a theory begins to arrive at that stage of development.

It's going to be a great conference! I gather you are in Spain, perhaps at the University in Madrid.
If your mind were at all open to non-string quantum gravity it would be lucky for you, you could learn something by attending.

 

[marcus]

Just to provide a little objective context for this conference, I will track the growth of Loop program in the past few years. The conference can be better understood if you realize the field has been in a phase of rapid growth. Yearly research output is one way to measure that.
This is number of Loop papers in successive years, using DESY keywords "foam, spin", "quantum gravity, loop space", and "quantum cosmology, loop space".

2005:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+DK+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3D+2005&FORMAT=www&SEQUENCE=citecount%28d%29 (41 papers)

2006:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+DK+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3D+2006&FORMAT=www&SEQUENCE=citecount%28d%29

2007:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+DK+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3D+2007&FORMAT=www&SEQUENCE=citecount%28d%29

2008:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+DK+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3D+2008&FORMAT=www&SEQUENCE=citecount%28d%29

2009:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+DK+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3D+2009&FORMAT=www&SEQUENCE=citecount%28d%29

2010:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+DK+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3D+2010&FORMAT=www&SEQUENCE=citecount%28d%29 (160 papers)

Another indicator would be the remarkable number of young researchers entering the field right now.
I can gauge that by the new names I see authoring papers, and by the new names on the list of participants at the Loops conference and the Zakopane QG school held this year (compared with QG schools other years.) Also from the jobs picture. I see people getting postdoc positions and faculty jobs in new places---new university and institute openings. The two indices show a change from say 5 years ago, and are probably related.

This is naturally going to help explain some of the energy in the conference. I think, by the way, that the Madrid organizers did a good job. The signs seem to point that way. We'll see more when it actually takes place.

 

[Sardano]

You know, your question makes sense! Thanks for asking. I am merely an outside observer with no connection with any research program, so normally it would not make sense for me to attend any of these conferences. But this one is so interesting I am almost thinking it was a mistake not to go! As a kind of "virtual journalistic webreporter" or some odd thing. Of course I don't mean that entirely serously. No I'm not going I have no realworld reason to go.

What I pity, we could meet, since I am going.

If you have examined the website you will have noticed an interesting thing about this conference. It welcomes rival theories.

Marcus, Marcus...you got all mistaken, there are no rival theories in science! All of them are interesting approaches that has to be pursued...Although I am aware that you are involved in a war agains ST. Thank God you don't represent LQG.

It is actually this parallel session which makes me wish that (even though I just observe the scene and don't have any involvement) I had made arrangements to go to Madrid.

You should came: aside from the conferences there is no better place to go on holidays, you would enjoy.

The other major new thing, I guess, is the strong showing at Loops 2011 of CMB (cosmic microwave background) phenomenology. The imminent prospect that real tests could constrain the theory. It causes excitement when a theory begins to arrive at that stage of development.

I doubt LQG is going to have any experimental test soom. But, who knows?.

It's going to be a great conference! I gather you are in Spain, perhaps at the University in Madrid.

You bet I am.

If your mind were at all open to non-string quantum gravity it would be lucky for you, you could learn something by attending.

Of course I am open to non string physics, not just QG. In fact, I am attending, so I hope I can learn a few thinks (probably about how wrong is LQG :) ). Anyway, what I don't buy is you personal war against ST and the way you talk about ST without having the basic knowdlege.

 

[marcus]

I doubt LQG is going to have any experimental test soom. But, who knows?.
...

I suppose it depends in part on what one means by "soon". Here are 32 Loop bounce phenomenology papers that have appeared 2009-now.
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+DK+QUANTUM+COSMOLOGY%2C+LOOP+SPACE%29+AND+%28DK+PRIMORDIAL%2C+FLUCTUATION+OR+DK+INFLATION+OR+DK+COSMIC+BACKGROUND+RADIATION%29+AND+DATE+%3E+2008&FORMAT=www&SEQUENCE=citecount%28d%29
They mainly discuss how to look for the imprint of Loop cosmology in the CMB polarization map. The important issue now is funding for a space mission like the proposed NASA "CMB-Pol". Given the economic realities it's hard to say how soon another CMB mapping instrument, following the current ESA "Planck", might be funded, and by whom.

Yes Madrid would be a wonderful place to visit. I would go immediately to see certain works of Goya and Hieronymus Bosch.

It is interesting to hear that you plan to attend this month's conference.

 

[marcus]

So much is in the air at this conference that it takes some concentration to remain aware of the main themes. I will list some:

A. Regge/Loop results
This refers to recent papers by Magliaro Perini and by Rovelli Zhang.
https://www.physicsforums.com/showthread.php?t=495473

B. Phenomenology (prospects for testing/constraining)
Predicted imprint of bounce on CMB-polarizaton map, to be found or not found.
See parallel session on Friday, 9 talks, many about this in particular.
Recent Loop pheno papers on arxiv (2009 and later):
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+DK+QUANTUM+COSMOLOGY%2C+LOOP+SPACE%29+AND+%28DK+PRIMORDIAL%2C+FLUCTUATION+OR+DK+INFLATION+OR+DK+COSMIC+BACKGROUND+RADIATION%29+AND+DATE+%3E+2008&FORMAT=www&SEQUENCE=citecount%28d%29

C. Shape Dynamics---duality with CFT (but not involving AdS)
4D gravity dual to 3D CFT.
Parallel session on Monday
https://www.physicsforums.com/showthread.php?t=494789

D. Relative Locality is not heavily represented. Only one invited talk and one other that I can see in parallel session.

@Anyone,
See if you can identify other major topics. Here's the program listing, with links:
http://loops11.iem.csic.es/loops11/index.php?option=com_content&view=article&id=75&Itemid=73

 

[Sardano]

It is interesting to hear that you plan to attend this month's conference.

Why? as a predoctoral researcher, I have to be aware of the latest developments in QG, and is a good oportunity to meet people from other branches of physics. And of course, my tutors project is paying ;).

 

[atyy]

Hmm, Dohse may talk about AdS/CFT. Maybe Zapata is secretly thinking about it too. Ryan is going to talk about some sort of holography!

It's interesting that Bahr and Ryan will both talk about group field theory. From their paper, I thought they were working on spin foams that didn't have a GFT dual, and now that I know what's behind Rovelli's TQFT and quantum groups madness, I like it perhaps more than GFT (though I still don't believe in pure quantum gravity). But I think Bahr and Ryan, and especially Dittrich, know where they are going.

 

[atyy]

Also, lots about spin foam coarse graining. Prima facie that's because the IP zero, J infinity limit is not exactly what is prescribed by Rovelli's theory.

I hope there will be different sorts of coarse graining, corresponding to limits of different sorts of physical measurement.

 

[murray92]

Is reuter or peracci giving a talk (Sorry I am to lazy togo through the shelude.
or anyone ele who does asymsafe gravity?

 

[atyy]

It appears there is consensus that LQG is divergent, and something must be done to fix it. http://arxiv.org/abs/1105.1334 , p8, from "The refinement limit considered in [RS10] envisions going to an “infinite complete 2-complex” and thus is of a significantly different nature." Hellmann cites a paper to appear by Bahr "Cylindrical consistency for spin foams" which is a proposal to cure the divergence. I would guess it follows up on ideas in http://arxiv.org/abs/1010.4787 , http://arxiv.org/abs/1010.5227 , http://arxiv.org/abs/1010.5437

Hellmann concludes "From our analysis it thus seems premature to claim that the lowest order terms show that there is a regime in which the theory reproduces cosmological spacetimes. Instead we find that the original calculation has to be reinterpreted as a calculation of the first topology changing spacetime."

 

[atyy]

Is reuter or peracci giving a talk (Sorry I am to lazy togo through the shelude.
or anyone ele who does asymsafe gravity?

Dario Benedetti: I present and discuss results of a 1-loop computation for the Einstein-Cartan theory, with the addition of the Holst term, proportional to the Immirzi parameter. As in the standard case, the theory is 1-loop finite, although non-renormalizable divergencies are expected at 2-loop order. Addition of fermions gives rise to non-renormalizable divergenices already at 1-loop, and more interestingly, it induces a running of the Immirzi parameter. I will discuss the meaning and consequences of these results, in particular in relation to the loop quantum gravity program.

The related paper is http://arxiv.org/abs/1104.4028

 

[murray92]

thanks

 

[marcus]

Atyy has added a handful of ideas to the list I gave earlier of what might turn out to be the main themes of the conference.

... it takes some concentration to remain aware of the main themes. I will list some:

A. Regge/Loop results
This refers to recent papers by Magliaro Perini and by Rovelli Zhang.
https://www.physicsforums.com/showthread.php?t=495473

B. Phenomenology (prospects for testing/constraining)
Predicted imprint of bounce on CMB-polarizaton map, to be found or not found.
See parallel session on Friday, 9 talks, many about this in particular.
Recent Loop pheno papers on arxiv (2009 and later):
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+DK+QUANTUM+COSMOLOGY%2C+LOOP+SPACE%29+AND+%28DK+PRIMORDIAL%2C+FLUCTUATION+OR+DK+INFLATION+OR+DK+COSMIC+BACKGROUND+RADIATION%29+AND+DATE+%3E+2008&FORMAT=www&SEQUENCE=citecount%28d%29

C. Shape Dynamics---duality with CFT (but not involving AdS)
4D gravity dual to 3D CFT.
Parallel session on Monday
https://www.physicsforums.com/showthread.php?t=494789

D. Relative Locality is not heavily represented. Only one invited talk and one other that I can see in parallel session.

@Anyone,
See if you can identify other major topics. Here's the program listing, with links:
http://loops11.iem.csic.es/loops11/index.php?option=com_content&view=article&id=75&Itemid=73

Hmm, Dohse may talk about AdS/CFT. Maybe Zapata is secretly thinking about it too. Ryan is going to talk about some sort of holography!

It's interesting that Bahr and Ryan will both talk about group field theory. From their paper, I thought they were working on spin foams that didn't have a GFT dual, and now that I know what's behind Rovelli's TQFT and quantum groups madness, I like it perhaps more than GFT (though I still don't believe in pure quantum gravity). But I think Bahr and Ryan, and especially Dittrich, know where they are going.

Also, lots about spin foam coarse graining. Prima facie that's because the IP zero, J infinity limit is not exactly what is prescribed by Rovelli's theory.

I hope there will be different sorts of coarse graining, corresponding to limits of different sorts of physical measurement.

It appears there is consensus that LQG is divergent, and something must be done to fix it. http://arxiv.org/abs/1105.1334 , p8, from "The refinement limit considered in [RS10] envisions going to an “infinite complete 2-complex” and thus is of a significantly different nature." Hellmann cites a paper to appear by Bahr "Cylindrical consistency for spin foams" which is a proposal to cure the divergence. I would guess it follows up on ideas in http://arxiv.org/abs/1010.4787 , http://arxiv.org/abs/1010.5227 , http://arxiv.org/abs/1010.5437

Hellmann concludes "From our analysis it thus seems premature to claim that the lowest order terms show that there is a regime in which the theory reproduces cosmological spacetimes. Instead we find that the original calculation has to be reinterpreted as a calculation of the first topology changing spacetime."

Dario Benedetti: I present and discuss results of a 1-loop computation for the Einstein-Cartan theory, with the addition of the Holst term, proportional to the Immirzi parameter. As in the standard case, the theory is 1-loop finite, although non-renormalizable divergencies are expected at 2-loop order. Addition of fermions gives rise to non-renormalizable divergenices already at 1-loop, and more interestingly, it induces a running of the Immirzi parameter. I will discuss the meaning and consequences of these results, in particular in relation to the loop quantum gravity program.

The related paper is http://arxiv.org/abs/1104.4028

Another main theme, I mentioned A-D so this would be E: The more central role now being played by SU_q(2).
The quantum version of SU(2) always used to be speculated about but it never seemed as central to Loop research as in the past year or so.

 

[marcus]

Atyy has added a handful of ideas to the list I gave earlier of what might turn out to be the main themes of the conference...
...
...Another main theme, I mentioned A-D so this would be E: The more central role now being played by SU_q(2).
The quantum version of SU(2) always used to be speculated about but it never seemed as central to Loop research as in the past year or so.

About SU_q, and also the q-deformed version of the Lorentz cover SL(2,C), it has appeared in many of the recent Loop papers. Including this by Wolfgang Wieland http://arxiv.org/abs/1105.2330
but also these by Muxin Han and Bianchi Rovelli:
==quote==
http://arxiv.org/abs/1105.2212
Cosmological Constant in LQG Vertex Amplitude
Muxin Han
(Submitted on 11 May 2011)
A new q-deformation of the Euclidean EPRL/FK vertex amplitude is proposed by using the evaluation of the Vassiliev invariant associated with a 4-simplex graph (related to two copies of quantum SU(2) group at different roots of unity). We show that the large-j asymptotics of the q-deformed vertex amplitude gives the Regge action with cosmological constant (in the corresponding 4-simplex). In the end we also discuss its relation with a Chern-Simons theory on the boundary of 4-simplex.

http://arxiv.org/abs/1105.1898
A note on the geometrical interpretation of quantum groups and non-commutative spaces in gravity
Eugenio Bianchi, Carlo Rovelli
(Submitted on 10 May 2011)
Quantum groups and non-commutative spaces have been repeatedly utilized in approaches to quantum gravity. They provide a mathematically elegant cut-off, often interpreted as related to the Planck-scale quantum uncertainty in position. We consider here a different geometrical interpretation of this cut-off, where the relevant non-commutative space is the space of directions around any spacetime point. The limitations in angular resolution expresses the finiteness of the angular size of a Planck-scale minimal surface at a maximum distance $1/\sqrt{\Lambda}$ related the cosmological constant Lambda.
This yields a simple geometrical interpretation for the relation between the quantum deformation parameter
$$q=e^{i \Lambda l_{Planck}^2}$$
and the cosmological constant, and resolves a difficulty of more conventional interpretations of the physical geometry described by quantum groups or fuzzy spaces.
Comments: 2 pages, 1 figure
==endquote==

Wieland, Han, Bianchi, and Rovelli are all in the Marseille group. What it looks like is that everything in Loop gravity coming out of that research team involves the quantum group---either as an approach to renormalization (getting convergence) or to including the positive cosmological constant (accelerated cosmic expansion: deSitter as opposed to Anti-deSitter)
=============================

Earlier I only saw one talk on the new idea Relative Locality, there are now two. They have added one by Laurent Freidel:
http://loops11.iem.csic.es/loops11/index.php?option=com_content&view=article&id=75&Itemid=73
==quote==
The Einstein localisation procedure in relative Locality.
Laurent Freidel
Central Room. Monday, May, 23rd, 17:00 - 17:20.
Abstract:
Relative Locality is a new framework in which the geometry of momentum space is non trivial and spacetime is a derived quantity reconstructed from the momentum space measurement. In order to do so we need to perform the Einstein Localisation procedure which usually allow to reconstruct spacetime from momentum space measurement. We show how this localisation procedure can be performed in Relative locality, how non trivial geometry in momentum space amounts to non locality in spacetime and show explicit physical effects that can be measured in the Gamma ray bursts observations, for instance.The Principle of Relative Locality.
Lee Smolin
Central Room. Thursday, May, 26th, 10:00 - 10:45.
Abstract:
A new principle is presented which we propose governs the phenomenology of quantum gravity in the regime where the Planck mass cannot be neglected. This involves a deepening of the relativity principle according to which the invariant arena for non-quantum physics is a phase space rather than spacetime. Descriptions of particles propagating and interacting in spacetimes are constructed by observers, but different observers, separated from each other by translations, construct different spacetime projections from the invariant phase space. Nonetheless, all observers agree that interactions are local in the spacetime coordinates constructed by observers local to them. This framework, in which absolute locality is replaced by relative locality, results from deforming momentum space, just as the passage from absolute to relative simultaneity results from deforming the linear addition of velocities. Different aspects of momentum space geometry, such as its curvature, torsion and non-metricity, are reflected in different kinds of deformations of the energy-momentum conservation laws. These are in principle all measurable by appropriate experiments, some of which will be described.
==endquote==

 

[atyy]

25th Anniversary of LQG Ceremony
Chair: G. Mena Marugán; Room: Central
12:00 - 12:45 25th Anniversary of LQG Ceremony

Will there be a birthday cake?

 

[marcus]

25th Anniversary of LQG Ceremony
Chair: G. Mena Marugán; Room: Central
12:00 - 12:45 25th Anniversary of LQG Ceremony

Will there be a birthday cake?

I'm positive there will be, Atyy. With ultraviolet frosting and 25 little infrared-colored candles.

 

[marcus]

Thiemann's abstract was posted today
http://www.iem.csic.es/loops11/
======quote=======
New Variables for Classical and Quantum (Super)gravity (LQSG) in all Dimensions.
Thomas Thiemann
Central Room. Tuesday, May, 24th, 10:00 - 10:45.
Abstract:
Supergravity in 10/11 dimensions is supposed to be the low energy limit of String/M Theory and should be in fact the semiclassical limit of any UV Completion of Supergravity. In order to compare String/M Theory with Loop Quantum Gravity it would therefore be very interesting to quantise Supergravity in 10/11 Dimensions with LQG methods. This was so far not possible because LQG is by construction a strictly 3+1 dimensional theory. In this talk we summarise recent results on how to pass the D+1=4 barrier and how to take first steps towards Loop Quantum (Super)Gravity (LQSG).
======endquote======

Abstracts from Thiemann's coauthors just went online today as well:
===quote===

Gauge Unfixing in Higher Dimensional General Relativity.
Andreas Thurn
M. Ambientales Room. Thursday, May, 26th, 15:25 - 15:45.
Abstract:
For matching spacetime and internal signature, we can rederive the connection formulation of General Relativity presented in the plenary talk by Thomas Thiemann starting from the Palatini action in any dimension. While the constraint set of this acton is known to contain second class constraints, we find an equivalent first class system by using the method of gauge unfixing. We demonstrate that the simplicity invariant extension of the Hamiltonian constraint, which is obtained when applying gauge unfixing, involves a correction term which is precisely the one found via the extension of the ADM phase space and which makes sure that the Hamiltonian constraint derived from the Palatini Lagrangian coincides with the ADM Hamiltonian constraint when Gauss and simplicity constraints are satisfied.

On the implementation of the canonical quadratic simplicity constraint.
Norbert Bodendorfer
M. Ambientales Room. Thursday, May, 26th, 15:45 - 16:05.
Abstract:
We are going to discuss a new approach to solve the quadratic simplicity constraints in the context of the recently developed canonical formulations of higher dimensional General Relativity and Supergravity. Since the canonical quadratic simplicity constraint operators are anomalous in any dimension D > 2, non-standard methods have to be employed to avoid inconsistencies in the quantum theory. We show that one can choose a subset of quadratic simplicity constraint operators which are non-anomalous among themselves and allow for a natural unitary 1-1 map to the SU(2)-based Ashtekar-Lewandowski Hilbert space in D = 3.

Towards Loop Quantum Supergravity: Rarita-Schwinger Sector.
Norbert Bodendorfer
M. Ambientales Room. Friday, May, 27th, 14:45 - 15:05.
Abstract:
We extend the recently developed canonical formulation of higher dimensional General Relativity to include Rarita-Schwinger fields (gravitinos) which naturally appear in Supergravities. Starting from a Hamiltonian formulation in the time gauge which yields a Spin(D) theory, a major challenge is to extend the internal gauge group to Spin(D+1) in presence of the Rarita-Schwinger field. This is non trivial because SUSY typically requires the Rarita-Schwinger field to be a Majorana fermion for the Lorentzian Clifford algebra and Majorana representations of the Clifford algebra are not available in the same spacetime dimension for both Lorentzian and Euclidean signature. We resolve the arising tension and provide a background independent representation of the non trivial Dirac antibracket *-algebra for the Majorana field which significantly differs from the analogous construction for Dirac fields already available in the literature.

Towards Loop Quantum Supergravity: p-Form Fields.
Andreas Thurn
M. Ambientales Room. Friday, May, 27th, 15:05 - 15:25.
Abstract:
We consider the quantisation of bosonic fields necessary to obtain a complete SUSY multiplet next to graviton and gravitino in various dimensions. As a generic example, we study concretely the quantisation of the 3-index photon of 11d SUGRA, but our methods easily extend to more general p-form fields. Due to the presence of a Chern-Simons term for the 3-index photon, which is due to local SUSY, the theory is self-interacting. We show that a reduced phase space quantisation with respect to the 3-index photon Gauß constraint is possible. Specifically, the Weyl algebra of observables, which deviates from the usual CCR Weyl algebras by an interesting twist contribution proportional to the level of the Chern-Simons theory, admits a background independent state of the Narnhofer-Thirring type.
==endquote==

 

[marcus]

Loops 2011: videos of plenary talks now online

VIDEOS are also available online for the LOOPS 2011 plenary talks.
Just select "Scientific Programme" from the menu and click on the title of a talk. This brings up the abstract of that talk. Below the abstract are links for video and slides.

I think SLIDES are available for all the talks. I checked for a fairsized sample to make sure. But video MP4 files only for the 36 or so plenary talks.

With the connection that I'm using, the MP4 file takes a rather long time to download. I have to start it downloading and go do something else.

If I have copied it correctly, the link for Rovelli's talk, for example, is

http://www.iem.csic.es/departamentos/qft/grupos/gravitacional/loops11/Archives/Plenary-Lectures/Videos/Carlo-Rovelli_The-covariant-version-of-Loop-Quantum-Gravity-definition-of-the-theory-results-open-problems.mp4