Freidel makes faculty at Perimeter

[marcus]

Laurent Freidel was postdoc at Perimeter for a while. As of recently he is faculty.

Now they have 3 faculty in non-string QG: Smolin and Markopoulou being the others.

 

[etera]

Laurent Freidel was actually "long-term visitor" in PI, not a postdoc. He's been a permanent researcher in France at the ENS Lyon for the past few years.

 

[marcus]

thanks for the correction, etera.

Congratulations on posting two interesting looking papers today yourself!

I have listed them in our bibliography thread
https://www.physicsforums.com/showpost.php?p=1069768&postcount=511
along with some other recent papers. If I had known
you were coming I would have thought of some questions to ask about these papers :-)

http://arxiv.org/abs/gr-qc/0608131
Group Integral Techniques for the Spinfoam Graviton Propagator
Etera R. Livine, Simone Speziale
16 pages

"We consider the proposal of gr-qc/0508124 for the extraction of the graviton propagator from the spinfoam formalism. We propose a new ansatz for the boundary state, using which we can write the propagator as an integral over SU(2). The perturbative expansion in the Planck length can be recast into the saddle point expansion of this integral. We compute the leading order and recover the behavior expected from low--energy physics. In particular, we prove that the degenerate spinfoam configurations are suppressed."

http://arxiv.org/abs/gr-qc/0608135
Towards a Covariant Loop Quantum Gravity
Etera R. Livine
13 pages, review, draft chapter for the book "Approaches to quantum gravity", being prepared by Daniele Oriti for Cambridge University Press, comments welcome

"We review the canonical analysis of the Palatini action without going to the time gauge as in the standard derivation of Loop Quantum Gravity. This allows to keep track of the Lorentz gauge symmetry and leads to a theory of Covariant Loop Quantum Gravity. This new formulation does not suffer from the Immirzi ambiguity, it has a continuous area spectrum and uses spin networks for the Lorentz group. Finally, its dynamics can easily be related to Barrett-Crane like spin foam models."

Etera can you give a guess, just off the top of your head, about when Freidel's next paper might be posted? I am beginning to get impatient to see how he extends things from 3D to 4D.

 

[etera]

Hello Marcus,
I have already seen a draft of their 4d paper, so i guess it is almost ready and that they will post it when Aristide (Baratin) will be back from holidays. I bet on the beginnning of october.

 

[marcus]

Hello Marcus,
I have already seen a draft of their 4d paper, so i guess it is almost ready and that they will post it when Aristide (Baratin) will be back from holidays. I bet on the beginnning of october.

Thanks. It's good news they have already gotten to that stage. I am glad to hear it!

I can imagine that the mood at Perimeter must be fairly cheerful and energetic at the moment. right after the conference at Penn State, with hopeful things happening like Freidel's appointment---and new papers.
If I am not mistaken you all must be having a good time these days!

It's neat that you and Speziale have the chance to collaborate. I think you two look like potentially a good team---if you both stay at the same place and are working in the same direction. The research picture has begun to look quite strong to me, as an outside (admittedly rather superficial) observer.

I actually wish I had dropped in as a visitor to the Penn State conference. Now I am curious about what the discussion was about in a few of the section---and I don't know any of the people in real life (only from reading) so it would be interesting to see them in person.

 

[john baez]

Three Cheers for Laurent! Three Cheers for Bob!

Laurent Freidel was postdoc at Perimeter for a while. As of recently he is faculty.

Wow, how did you find that out? I didn't even know, and I wrote him a letter of recommendation.

Speaking of good news of this general sort: http://web.comlab.ox.ac.uk/oucl/people/bob.coecke.html" teaches. As you know, their work combines category theory and quantum mechanics in a way that's mathematically very related to loop quantum gravity, but applied to quantum computation.

Bob says http://www.maths.gla.ac.uk/~tl/" got the same sort of 5-year postdoc up in Glasgow a while ago. So, category theory is doing well in the UK!

Bob recently turned up at a http://golem.ph.utexas.edu/category/2006/08/quantum_computation_and_symmet.html" , and we got to talking... that's how I know this stuff.

 

[marcus]

hello John Baez,
how I knew was I just happened to check the main welcome page at P.I. site that day and it said congratulations to Laurent.
(turns out I was wrong about his being postdoc before, he was longterm visitor)

really nice of you to happen in here now and then! for plain human reasons---it seems that my brain is ossified enough I can't really learn about e.g. Cartan connections and about 2 groups. I have moments of understanding and then the next day have forgotten how---and I inevitably say things like isometric instead of isomorphic. But to let you know that even the confirmed unteachable value your posts.

===============
BTW the 5-year postdoc position
yes I'm persuaded that Bob coecke is very smart and also highly independent driven and creative, so that would be a good one to give a 5 year contract
what it reminds me is what Lee Smolin keeps saying is his message----he keeps saying that he is not criticising string dominance except as an example and that what he wants is to give longterm support to creative independent motivated people with a good trackrecord REGARDLESS OF WHAT LINE OF RESEARCH THEY PICK and have it depend on the individual and not on their belonging to the dominant program. So you trust the capable welltrained people to go their own way.
This seems like a no-brainer. Almost ask, why does he even have to argue for that?

But anyway maybe that is an example of a system working. Coecke can now go explore his own private Wilderness of Lovely Wonders for a whole 5 years. We are all likely to benefit from this, one way or another. It is the proper thing to happen.

 

[francesca]

gossip

... and Daniele Oriti is moving from Cambridge to Utrecht!
Holland is a good place to do QG

 

[marcus]

... and Daniele Oriti is moving from Cambridge to Utrecht!
Holland is a good place to do QG

thanks for the gossip

I am stunned actually. I thought he would do Cambridge a lot of good. He seemed suitable.
Now Loll's team has some people you really have to look out for.

Starodubtsev, Hanno Sahlmann, and that young causal sets guy, I forget the name.

Maybe Oriti will be in that group too. I don't understand the strategy. Why has Loll, if it is Loll who is actually doing this, gathered these people.

they are the best who are on the loose---in non-string QG---at least to a reasonable approximation.

where do they get the money and the moral support institutional wise?

it does not have to do directly with Loll's main research direction, or with 't Hooft either------do they believe in creative anarchy?

it's very interesting. thank you so much Francesca!

oh yes Frank Saueressig is there also---he has Martin Reuter connections.
and Serguey Alexandrov. something of an enigma.
these are all young PhDs

 

[selfAdjoint]

thanks for the gossip

I am stunned actually. I thought he would do Cambridge a lot of good. He seemed suitable.



Now Loll's team has some people you really have to look out for.

Starodubtsev, Hanno Sahlmann, and that young causal sets guy, I forget the name.

Maybe Oriti will be in that group too. I don't understand the strategy. Why has Loll, if it is Loll who is actually doing this, gathered these people.

they are the best who are on the loose---in non-string QG---at least to a reasonable approximation.

where do they get the money and the moral support institutional wise?

it does not have to do directly with Loll's main research direction, or with 't Hooft either------do they believe in creative anarchy?

it's very interesting. thank you so much Francesca!

oh yes Frank Saueressig is there also---he has Martin Reuter connections.
and Serguey Alexandrov. something of an enigma.
these are all young PhDs

Mmmm, I recall Sahlmann as an ingenious transformation rainmaker, an indispensable type and nowhere as numerous as they used to be when grad students cut their teeth reproducing the entries in the tables of integrals. We should look at thee people in terms of their skills and talents as well as there theortetic backgrounds.

 

[marcus]

Maybe Francesca knows something more, but hasnt said.

AFAIK the non-string QG postdocs at Utrecht are not necessarily doing Loll's special program CDT. they appear to be researching whatever they damn please

the Causal Sets guy, I remember now, is named Joe Henson.

at first when I saw the list of Loll postdocs, as of September 2005, I thought she had brought these people like Henson and Sahlmann over into Dynamical Triangulations QG (this is how naive I am) but this has not happened at all.

it is just a bunch of proven good non-string QG people who get to work in whatever direction they want.

(AFAICS----which I think must be less and less far and less and less clearly )

BTW was reading John Barrett's latest right after my afternoon nap.
Hppy Lbor Day! It's cool and sunny. http://arxiv.org/hep-th/0608221
A Lorentzian version of the non-commutative geometry of the standard model of particle physics

you know the story of the several blind men that had hold of various parts of the elephant and had various things to say about it.

what did the blind man say who had hold of the BALLS of the elephant?

 

[marcus]

that's not a serious question. I'm hoping nobody thinks what to answer.

 

[john baez]

I thought he would do Cambridge a lot of good. He seemed suitable.

Oriti didn't have any sort of permanent or "tenure-track" position there - he was just a http://www.damtp.cam.ac.uk/user/do001/", and now he's moved on to his next postdoc with Loll at Utrecht.

(I put "tenure-track" in quotes because they don't have tenure in the American sense in Britain.)

Now Loll's team has some people you really have to look out for.

Yup.

Maybe Oriti will be in that group too.

Yes, he will be.

I don't understand the strategy. Why has Loll, if it is Loll who is actually doing this, gathered these people.

It's obviously a good thing to do. More importantly, she's got the means to do it! Read her http://www.phys.uu.nl/~loll/Web/title/title.html":

In December 2004, Loll won a five-year VICI award by the Netherlands Organisation for Scientific Research (http://www.nwo.nl/nwohome.nsf/pages/NWOP_67vcbu?Opendocument" ), which brings together 13 European research groups working on theories of random geometry, with applications ranging from quantum gravity and string theory to dynamical networks in biology and econophysics.
​

Serious business!

 

[john baez]

hello John Baez,

how I knew was I just happened to check the main welcome page at P.I. site that day and it said congratulations to Laurent.

I see!

(turns out I was wrong about his being postdoc before, he was longterm visitor)

Yeah, I know.

really nice of you to happen in here now and then! for plain human reasons---it seems that my brain is ossified enough I can't really learn about e.g. Cartan connections and about 2 groups.

It's mainly a matter of the difference between spending 70 hours a week on something, and spending less time on it.

I have moments of understanding and then the next day have forgotten how---and I inevitably say things like isometric instead of isomorphic.

Don't worry about it - it's no big deal!

But to let you know that even the confirmed unteachable value your posts.

Thanks! Though I'm not sure you're in that category.

Re Coecke:

what it reminds me is what Lee Smolin keeps saying is his message----he keeps saying that he is not criticising string dominance except as an example and that what he wants is to give longterm support to creative independent motivated people with a good trackrecord REGARDLESS OF WHAT LINE OF RESEARCH THEY PICK and have it depend on the individual and not on their belonging to the dominant program. So you trust the capable welltrained people to go their own way. This seems like a no-brainer. Almost ask, why does he even have to argue for that?

Indeed! Unfortunately, academics are hired, promoted, and given grants by their peers - nobody else can really judge them - and this easily leads to "groupthink": most people tend to favor people who are doing things like themselves. This is okay to some extent, but if one faction expands to monopolize the resources it can be dangerous.

But anyway maybe that is an example of a system working. Coecke can now go explore his own private Wilderness of Lovely Wonders for a whole 5 years. We are all likely to benefit from this, one way or another. It is the proper thing to happen.

Yes! I'm going to try to visit him next summer if he's not running around to too many conferences. I'm getting really excited about http://golem.ph.utexas.edu/category/2006/09/doctrines.html" , which is just the sort of stuff he's doing with Abramsky at Oxford.