Quantum Graffiti: MEDIA COVERAGE, JOB OPENINGS & Gossip Around Loll at Utrecht

[Smots]

VEry nice! Thanks for that nice book :).

 

[marcus]

Hey Quirine!
just saw you were here visiting us at PF!
arent you the physics student on Loll's team, who has a sculptor in the family?
sculpture is good background for physics---concrete and visual!
any news from the website competition?

===================
I better update the Loll/Utrecht news:

Loll just posted two papers that I didnt record here yet. here is one with Dario Benedetti
http://arxiv.org/abs/hep-lat/0603013
Unexpected Spin-Off from Quantum Gravity
D. Benedetti (U. Utrecht), R. Loll (U. Utrecht)
10 pages, 4 figures

"We propose a novel way of investigating the universal properties of spin systems by coupling them to an ensemble of causal dynamically triangulated lattices, instead of studying them on a fixed regular or random lattice. Somewhat surprisingly, graph-counting methods to extract high- or low-temperature series expansions can be adapted to this case. For the two-dimensional Ising model, we present evidence that this ameliorates the singularity structure of thermodynamic functions in the complex plane, and improves the convergence of the power series."
============

here is one with Willem Westra

http://arxiv.org/abs/hep-th/0603079
Nonperturbative sum over topologies in 2D Lorentzian quantum gravity
R. Loll (U. Utrecht), W. Westra (U. Utrecht), S. Zohren (U. Utrecht, RWTH Aachen)
10 pages, 4 figures. Talk given by S. Zohren at the Albert Einstein Century International Conference (Paris, July 18-22 2005)

"The recent progress in the Causal Dynamical Triangulations (CDT) approach to quantum gravity indicates that gravitation is nonperturbatively renormalizable. We review some of the latest results in 1+1 and 3+1 dimensions with special emphasis on the 1+1 model. In particular we discuss a nonperturbative implementation of the sum over topologies in the gravitational path integral in 1+1 dimensions. The dynamics of this model shows that the presence of infinitesimal wormholes leads to a decrease in the effective cosmological constant. Similar ideas have been considered in the past by Coleman and others in the formal setting of 4D Euclidean path integrals. A remarkable property of the model is that in the continuum limit we obtain a finite space-time density of microscopic wormholes without assuming fundamental discreteness. This shows that one can in principle make sense out of a gravitational path integral including a sum over topologies, provided one imposes suitable kinematical restrictions on the state-space that preserve large scale causality."

 

[Quirine]

Team Loll

Hi there,
Yes I'm indeed a member of the team
First I want to apologize for the very bad English,
It is really funny to read that some of you are following our weblog,
I red that there were a few questions about my name. So I'll give a quick answer to them.
No I'm not related to the famous (well in the Netherlands he is) weather man Erwin Krol. Also my mother is not a sculptor. I'm just an extract of a two musicians, nobody ever heard of.
You also wanted to know who TL was? It stands just for Team Loll. All the drawings are in fact made by Egbert Rijke. We are lucky to have him in our team.
The three youngest of the group (me included) are not following any course for this project,we are just interested in Renates theory and we do all this in our spare time. I'm really glad to have this upportunity.
so if there are any questions, ask them, I'll see what I can do,
greetings,
Quirine

 

[marcus]

Hey People!
this is great! we have a Physicsforums contact with Loll's team of Utrecht students.
Hello Quirine,
no I don't have any questions just now, but please look in from time to time---maybe I or somebody will think of some things we want to know that you can tell us!

several of us here also, like you, are interested in Loll's CDT approach to exploring the fundamental nature of spacetime

also Renate Loll kicks butt-----and she writes pretty good English too.

is it alright to post this SONS link
http://www.phys.uu.nl/~sons/index.php?option=com_content&task=view&id=16&Itemid=56
it has your student organization photo so we can have an idea how you look
if this is not OK, say and I will erase the link

(it is all right to be from musicians family, I am right now listening to a clarinet quintet in A major by Mozart, he liked the clarinet and used to play it himself and he wrote some sweet music for it)

 

[marcus]

Quirine, I just had a thought. Is there anything you would like US to think about or try to explain? you have indicated that we could ask you questions about Team Loll and your website competition, and you would try to answer.

we can reciprocate and say is there anything you would like us to try to explain? (we might not be able to but we could attempt it )

For example. I find Willem Westra work on topology-change very interesting. It allows spacetime to be frothy, like beer. or seltzer water.
you, Quirine, could ask us to explain WHY we think modeling microscopic very brief topology change in the Loll path integral is interesting. We could try to explain.

It is just an idea, maybe it would not work (after all, I am just an interested observer, not a QG expert).

 

[Quirine]

that would be great, because for me it's only an vage intuition why this all makes sense.
Eversince I was a kid Triangles were very interesting. From Pyramids to geometry on secundary school. There was also a course where you must build our own dream house.. geuss what? Mine was build of tetrahedrons... Then I went to the University of Utrecht and there was suddenly Renate Loll with her triangulations, it catched my eye immediately.
So if you would be very kind to explain some things it would be really great

 

[marcus]

...so if there are any questions, ask them, I'll see what I can do,
greetings,
Quirine

actually I have a question.
I am very curious to know something, if it is not awkward or inappropriate to be asking

I want very much to know how Willem is coming in the project to extend the topology-change result from 2D to 3D (or, if we could be so fortunate to 4D!)

my feeling is that it will be very hard to extend the result! I would like to know if there is any progress

 

[Quirine]

well, I'm afraid I can't answer this technical questions myself, I would ask Willem to do so, but we all are running out of time, especially Renate en Willem, so I think you have to wait for that kind of answers. Maybe next year I will understand a bit of this all, but I think you can't wait for that...
In this case I will ask Willem tomorrow for a answer that I can understand and which I can tell you... Do you want to know it mathematically? Or Physically?
Renate explains this thing to other people, she uses a piece of paper which she crumples. It depends on how deep you look how many dimensions you measure/calculate. The strange thing about it is that you can also have solutions that varies from 2 till 3 dimensions, but I think you knew this already

 

[marcus]

So if you would be very kind to explain some things it would be really great

it probably is not efficient for me to try to explain the basics of Loll's approach, you can get better teaching close to home!

but I can talk about some aspects, like why is Westra's work so interesting.

AFAIK (abbreviation for As Far As I Know) there is no other quantum model of spacetime that can handle the appearance of microscopic suddenly appearing and vanishing holes and bubbles in space.

Other QG models I think can only handle a spacetime that is like a continuous block-----the block can have a changing geometry, like Jello, that can bend and tremble-----but it cannot suddenly get a hole

in other QG models you cannot have suddenly tiny holes and tunnels that suddenly come into existence and then flicker out of existence.

but in Loll QG, if it is simplified down to a 2D world, you CAN have!

like a little bubble that appears for a moment and then goes away

the word that I think of is FIZZY, a space that is fizzy, like I remember my first drink of ginger ale, or so-called "sparkling water" the tiny bubbles are like sparks. you feel them prickly on the tongue

if Loll and Westra do not succeed in extending this fizziness to higher dimension that will still be OK-----the CDT is still a very good interesting approach

but if they succeed, then that would be a way in which the CDT approach is special, it would make it stand out before all others (AFAIK)having holes and bubbles and tunnels that are very tiny, and which exist only for a moment, is an example of something that is called TOPOLOGY CHANGE
and so one can look back in the ARXIV (a kind of electronic online library) and find the 2003 papers of Loll and Westra about topology change in the 2D version of CDT.

they call it "topology change" because this sounds more serious than if they call it "fizzy spacetime"

be careful, maybe i am wrong or giving you the wrong idea.
check with Westra if this is the right picture

I am listening to an old recording of MOZART figaro sung in german by anneliese rothenberger, hermann prey and walter berry and the dresden philharmonic it is ABSOLUTELY FANTASTIC

 

[marcus]

Do you want to know it mathematically? Or Physically?
...

Physically!

but actually, don't worry
if you are running short of time, don't bother with my question
just focus on what you have to do, the rest will easily wait

(sorry did not see your post until just now)

it is late at night there, yes?

 

[marcus]

the Utrecht team has put up another chapter

http://www.academischejaarprijs.nl/utrecht/?p=9#more-9

with more of Egbert's drawings.

 

[marcus]

Loll has an interview in the March 2006 Dutch edition of the Scientific American

http://www.phys.uu.nl/~loll/Web/press/RLoll_in_Sciam.pdf

4 pages, photographs, popular style writing (staple SciAm)

I wish we had a translation, of at least some highlights. It's all in Dutch
and babelfish usually doesn't do a very good job of automatic translation *gloom* :(

 

[Pietjuh]

If I find the time tonight, I will try to create a decent translation of it all. It's a long interview, so perhaps I will do it in a few installments.

(perhaps I should promote myself to Loll-translator)

 

[marcus]

If I find the time tonight, I will try to create a decent translation of it all. It's a long interview, so perhaps I will do it in a few installments.

(perhaps I should promote myself to Loll-translator)

WOW THAT WOULD BE SO GREAT!

Don't be afraid to be selective either. If you are willing to translate even some----the parts you find most interesting or entertaining---that is also a big favor to us. Thanks!

 

[Pietjuh]

The bubblebath of the cosmos


Madame Loll, why hasn't the physics at the Planck scale used causality earlier on?
There was a good reason to do it. It considerably hard to build models of spacetime. By ignoring causality, the job became a lot easier.

A typical case of intellectual laziness?
Oh no, not at all. By simplifying the task, people were suddenly able to do calculations which were impossible before. From this one could also get very meaningfull results, despite taking assumptions you can't completely justify. This is always better than doing nothing at all. You should ofcourse look back at a certain moment en question if that simplification is still justifiable.

You thought that ignoring causality is no langer justifiable.
Doubting causality is ultimately just whishful thinking. Stephen Hawking hasn't made much progress in the last 25 years working on his research about the quantumstructure of spacetime -- and that's not even a controversial statement from myself!

Why do we need quantum foam?
On lower and lower scales quantumfluctuations will become increasingly intense. Some people say that these fluctuations will go look like a bubblebath, or even that they can rip spacetime apart. Although these are just metaphores. Realize that quantumfoam is a very vague concept! It isn't a classical phenomenon. We know that on the smallest scale something violent is happening to spacetime, and this unknown phenomenon is given the name quantumfoam.

Driehoekjes

You are constructing your model of quantumfoam with triangles. Why choose this shape?

The shape isn't that important actually. It's just a tool to build a model of spacetime. Eventually it doesn't matter which shape you use - triangles, squares or other shapes. My building blocks are in fact just imaginary substructures and are often misinterpreted. Consider that my building blocks are much smaller than the Planck scale.

You are saying that to do chemistry experiments, you don't need a precise model of the structure of protons and neutrons.
Exactly. Besides, the choosing of the building blocks isn't the most difficult task. For example, I can create all kinds of structures with Lego bricks, that's fairly easy. But to create a moving structure is already a lot harder. That's also the case with the creation of a model of spacetime.
The building of such a structure is one thing, but to find out how such a structure quantumfluctuates is a lot harder. We have good reasons to assume that the dynamics of spacetime don't depend much on the type of building block.

How do you calculate such a model of spacetime?
We don't do a straightforward calculation, but use the principle of superposition. Imagine you want to know how a special little particle moves aroung - a particle so small that quantumeffects play a role. You can't assume that the particle just moves in a straight line from A to B. We therefore must describe the movement as a scala of possible routes such a particle may take - say a probability cloud of the movement. The sum of all those paths eventually gives you a good quantumdescription of the particle. In principle we do the same with spacetime. We take a large sum of all possible spacetimes. But naturally spacetime is much more complex than the movement of one particle.

By Thor! How does such a result look like?
You certainly have to ask yourself really good what kind of questions you ask, what you eventually want to calculate. And that's not an easy excercise. For example, you can ask yourself how you can determine the number of dimensions of the object you are calculating. There are several methods to do this. We can put, for example, extra building blocks in the model, to see how they spread in spacelike directions, but also in timelike directions. The dimensionality of the object follows from this spread.

 

[marcus]

(perhaps I should promote myself to Loll-translator)

Yes! Congratulations on your promotion! I hope you have some idea what a help it is. I like what Loll is saying here. It gives a fuller perspective on her research than what one gets by only looking at the journal articles. This is what the Scientific American magazine is good for! Many thanks, Pietjuh.

Here is the original Dutch SciAm article link, if someone wants to see the photographs or puzzle over what is the dutch word for "bubble bath" and stuff like that.

http://www.phys.uu.nl/~loll/Web/press/RLoll_in_Sciam.pdf

BTW I can read a few words, so I see from the bio-box that she was born in 1962 and studied in Freiburg and London, and has a son.

Also I see that in some of the un-translated parts she is talking about string theory, but I cannot quite tell what she is saying about it.

 

[Pietjuh]

Also I see that in some of the un-translated parts she is talking about string theory, but I cannot quite tell what she is saying about it.

The interviewer asks what the link is between string theory and CDT, and specificaly about the difference in dimensions. She answers that the 2 theories have totally different starting points, and she doesn't want to elaborate on the experimental verification of string theory and CDT.

Then the interviewer asks if she believes there could be 11 dimensions. The answer is a bit vague, she thinks there might be some positive outcome from theories with extra dimensions because people have been working on it for so long.

The final part on the interview is mostly about things Loll doesn't know. They ask her how energy is incorporated in her theory. She says she simply doesn't know it yet, but she hopes that in the future she might be able to use CDT to explain dark matter.

 

[marcus]

schedule of Loll talks

thanks Pietjuh!
for the summary as well as the translation.
I see you are at Leiden. this spring Loll had two talks scheduled at Leiden (8 March and 3 May). I don't remember if you said about this---did you happen to attend the 8 March?

I see that Laurent Freidel is talking at Utrecht on 1 May.
If anybody here can make it please do. You will not be disappointed he is doing exciting research and has a clear focused delivery.

Also if you go then please report to us some highlights of the talk or what the general message is. It is time for Freidel to be saying something about the 4D case, can he extend some of his 3D results.
Some weeks back, he had a paper with Baratin in the works, some implications for QG from feynman diagrams IIRC. Maybe he will refer to this paper in his talk.
=================
this month, April, Frank Saueressig (the name is easy to remember because it means sour vinegar) is giving a talk at Utrecht. Saueressig has co-authoried with Martin Reuter, who does QEG (quantum einstein gravity, asymptotically safe gravity) and who has found lower dimension at Planck scale.

Possibly Saueressig could say something about QEG in his talk. Notice that both Jacques Distler (hostile comments) and John Baez (not so hostile) have discussed Reuter's work. Baez talked about it in TWF #228 just this past month (mid March). Baez said as it stands the work depends on a rough approximation and so some conclusions might be wrong, but that it was interesting and should be studied some more. Maybe one can improve the approximation and see if the conclusions still hold.

To anyone at Utrecht: if you hear Frank's talk on 27 April, please tell us what it is about.
===============

Renate Loll is now giving talks at various universities at a rate of about one per month:
Feb 24 Physics colloquium Utrecht University, The Netherlands

Mar 8 Conference talk Workshop "The World a Jigsaw - Tesselations in the Sciences", Lorentz Center, Leiden, The Netherlands

Apr 4 Conference talk ENRAGE Network Conference-cum-Workshop, International Centre for Mathematical Sciences, Edinburgh, UK

May 3 Ehrenfest Colloquium Leiden University, The Netherlands

Jun 8 Conference talk Theory CANADA 2 Conference, Perimeter Institute, Waterloo, Canada

================
It is interesting that Loll will give a talk in June at the CANADA conference. It suggests that she will be based at Perimeter sometime this spring or summer, on a working visit.

the Canada conference is not an international conference. One would not invite someone to come from Holland just to give a talk. But Bianca Dittrich who is from Germany HAPPENS to be currently a postdoc at Perimeter and so she is giving a talk at this conference. Since Loll will be speaking I tend to assume that she will be temporarily based there and doing some work at Perimeter around that time.

 

[Pietjuh]

I wasn't able to attend the talk in march, because I didn't know she had one! Thanks for pointing out she's also giving one at the general colloquium in may. I certainly plan to visit it!
I'm also seriously considering to apply for 'graduate school' at the university of Utrecht, because of the really interesting research that is being done there in theoretical physics. Here in leiden it's more oriented on condensed matter physics and biophysics.

 

[marcus]

...Here in leiden it's more oriented on condensed matter physics and biophysics.

condensed matter is a growth area in physics research
and so (I think) must be applied physics related to bio, and medicine.
maybe the Leiden people are practical and smart, so they focus on areas that have plenty of career satisfaction and growth possibilities.

I am retired, and don't have to worry about these things. Also have idealistic non-practical tendencies. To me, investigating the fundamental nature of spacetime-and-matter is a great adventure. like going to the North Pole, or the South Pole used to be. but I would never ADVISE a young person to go into it----only if they have a passionate interest already and must do it.

otherwise I would say
1. astrophysics
2. condensed matter
3. bio and medicine-related
not necessarily in that order.

How did you get to become a reptile caretaker? I suppose that could mean either one of two things, that you are a reptile who takes care (possibly of humans) or a human who takes care of reptiles

I envy you because you live in Holland, which seems like a nice place, and are near Utrecht.

How long a drive is it from Leiden to Utrecht?

Laurent Freidel's talk at utrecht (at the Grafiti seminar that Loll organizes) on 1 May could turn out to be an important talk.

here is Loll website, and the seminar page:
http://www.phys.uu.nl/~loll/Web/title/title.html
http://www.phys.uu.nl/~loll/Web/seminars/seminars.html

It says that the Grafiti seminar is in room MG 401
and scheduled for Monday at 2PM

I think the next 5 years of advances in QG (including matter) will have a lot to do with computer simulation
"monte carlo" (which means randomized) simulation of histories of toy universes-----or random histories of chunks of spacetime-and-matter.
Loll has be one of the first to do these monte carlo simulations.
but they may also be done with OTHER kinds of models----like those that Laurent Freidel is investigating

Loll says that "Grafiti" stands for "Gravity-and-Fields-Tea"
so there is probably some tea to drink before or after the talk

 

[Pietjuh]

condensed matter is a growth area in physics research
and so (I think) must be applied physics related to bio, and medicine.
maybe the Leiden people are practical and smart, so they focus on areas that have plenty of career satisfaction and growth possibilities.

The slogan here at the physics department of leiden is "Van meten tot weten", which roughly translates into "From measuring to knowledge". Here they don't concern themselves much with the fundamental issues of nature, but are a bit more down-to-earth in their research topics. We have a pretty large condensed matter group, mostly consisting of experimental groups and a small theory group. We also have a pretty good astroparticle physics group led by Ana Achucarro (she is also my advisor for my bachelorthesis on representation theory in elementary particle physics)

There are also many advantages for staying in leiden to do my masters degree, because here I'm garantueed to get a place, and I will not lose my job at the university as a teaching assistant (i need the money to pay my violin lessons).

How did you get to become a reptile caretaker? I suppose that could mean either one of two things, that you are a reptile who takes care (possibly of humans) or a human who takes care of reptiles

I envy you because you live in Holland, which seems like a nice place, and are near Utrecht.

How long a drive is it from Leiden to Utrecht?

I've always been interested in animals and seriously considered to pursue a degree in zoology, or marine biology. Last year I discoverd there was a small reptile/amphibian zoo in Delft, so I contacted them for a volunteering position. It's really a great "job", you get to know a lot of animals and how they behave and experience handling them.

Holland certainly is a nice place, but a bit too crowded in the area of the major cities. The east on the contrary, bordering germany or luxenburg/belgium is a nice landscape, with lot's of wildlife! (with the only poisinous snake species in the country!).

The drive to Utrecht isn't that far. If I take the train it takes about 35 minutes to get to the central station, and then i think about 10 minutes by coach to the faculty. Leiden is pretty central to most cities, like amsterdam, den hague and rotterdam. Amsterdam and rotterdam are all about 30 minutes with the train, and den hague is just 10 minutes from Leiden (in summers it's nice to take the bike and cycle across the dunes to den hague :) ) Leiden is also a pretty small town, with aproximately 100.000 citizens.

 

[marcus]

Yesterday I was looking at the current list of seminars at the Utrecht ITP
and it came to me why I approve of Renate Loll---two reasons why.

1. she gets young people to volunteer to take responsibility for things
2. she is a team player

look at the evidence. Loll's QG line is dynamical triangulations and, in Fall 2005, she had 3 postdoc positions to give

shall she give out these postdocs to people who will do Loll-type Triangles gravity? or shall she give them out in a way that is good for the whole field of QG?

watch.

the most outstanding young person in the Causal Sets line is Joe Henson.
the most outstanding young person in canonical Loop line is Hanno Sahlmann

if you compartmentalize, you think Hanno should be at Golm or Penn State, you think Joe should be in London with Fay Dowker. You would think neither would be any good to Loll, in a narrow Triangulations sense.

But in Fall 2005, Loll surprises you and invites Henson and Sahlmann to Utrecht (share the job of supporting the young researchers in a field-wide way, don't be parochial) and now what happens?

heh heh.

Now, Spring 2006, every week at the Utrecht ITP, Henson and Sahlmann are teaching a seminar on SPIN FOAMS. that is what is so funny. neither of them have done research on that. how did they get the idea? maybe Loll suggested to them that they should learn that approach. or maybe the two of them just got the notion to do it.

Spinfoam is the approach that Laurent Freidel uses, and Etera Livine and Daniele Oriti, and lately Carlo Rovelli (to make graviton propagators). And UTRECHT DOES NOT HAVE ANY spinfoam people.

All right Joe and Hanno, you be our spinfoam people. this tickles me. I am amused and delighted by it. they don't just serve the house brand at Utrecht. they bring canonical Loop and Causal Sets people in for postdocs and then they have them do yet another thing: spin foam. Probably it is very hard for those two postdocs, which is good for them. they are better off there than in Berlin or London, I think.

I would not be surprised if in their seminar they are studying the new Freidel Baratin paper. And they will be ready when Freidel comes to utrecht to give a talk on 1 May.

This is why non-string non-perturbative quantum gravity is ONE FIELD, instead of several separate little fields---social behavior like this makes it one field.

I first saw this aspect of Loll's behavior when she was invited to give a paper at the Paris July 2005 Einstein Centennial Conference. She sent an UNDERGRADUATE named Stefan Zohren to deliver a paper which is essentially the THESIS research of another student of hers named Westra. So she was pushing her youngest up to the firing line. And then, that Fall, she packed Zohren off to spend time with Fay Dowker and Chris Isham in London.

Loll could have given a major paper of hers at Paris. Instead she spun off from Westra's thesis a paper with three authors: Loll, Westra, Zohren---and she had the most junior author deliver it. And then go off to grad school at London Imperial. this has to be a good people-policy.

BTW in case anyone is curious about the paper Zohren gave in Paris, it was just posted last month on arxiv
http://arxiv.org/abs/hep-th/0603079
Nonperturbative sum over topologies in 2D Lorentzian quantum gravity
R. Loll (U. Utrecht), W. Westra (U. Utrecht), S. Zohren (U. Utrecht, RWTH Aachen)
10 pages, 4 figures. Talk given by S. Zohren at the Albert Einstein Century International Conference (Paris, July 18-22 2005)

 

[Pietjuh]

When I was talking to some professors today, we came to the subject of Renate Loll. The funny thing is that they said she is a bit in a lonely position there in utrecht, despite all the publicity she gets. But they found it really great she just went on in her own way :)

 

[marcus]

Freidel talk 1 May announced

Loll organizes two seminar series, and one is called "Grafiti" Gravity and Fields Tea

Grafiti #123 will be Laurent Freidel
https://www.physicsforums.com/showthread.php?p=968337#post968337

It will be an important talk, try to hear it if you live in Utrecht and can make the time.

He will probably say something like this:

we have a model of 4D spacetime which gives rise to matter
by reproducing the feynman diagrams of quantum field theory in its zero-gravity limit

and this model is TESTABLE because it requires a certain type of NONCOMMUTATIVE GEOMETRY which involves a testable variation in the speed of light at high (but currently accessible) energies

The theory will not work otherwise. So this theory of spacetime and matter is vulnerable to refutation if the slight variation in the speed of light is NOT observed.

shahn majid (who has co-authored with Freidel) has already announced this prediction.
==========================

My personal opinion is that would not be so smart now for someone to say "oh well I think that variation of speed will not be observed" or "oh I think it is a good theory and I imagine that it will be observed." It does not matter now what you or I THINK will be: the experiment matters. The point is that we are now entering an empirical stage of Quantum Gravity and thankgoodness there is finally something testable.

even if it be a risky long-shot, I respect it because it is falsifiable with available instruments at accessible energies! And they have made a definite prediction.
=========================

that is what I think Freidel's 1 May talk will be about and I will be disappointed if he only recapitulates the work in 3D which led to the same conclusion. Only when extended to 4D can the results give a prediction about what will be seen by the 2007 GLAST satellite.

===========================

the logical connections are

SPINFOAM GRAVITY <===> EFFECTIVE FIELD THEORY <===> NONCOM-GEOMETRY <===> SATELLITE OBSERVATIONS

====================
the announced title of Freidel's 1 May Utrecht talk is

Non-commutative Effective Field Theory and Quantum Gravity

the time is 2 PM in the Minnaert building, if I remember right
be there or be square

 

[marcus]

Freidel is giving his talk right about now in Utrecht

"Non-commutative effective field theory and quantum gravity "

It was scheduled for 1 May 2PM Dutch time, at the Minnaert building.

Did anybody get to hear the talk? It would be interesting to get any report.

 

[marcus]

Frustratingly enough, Renate Loll looks to be running the best series of QG seminars in Europe and we don't hear about them or see anything online

May 1 Grafiti no.121 Laurent Freidel (Perimeter/Lyon) Non-commutative effective field theory and quantum gravity

May 18 Quist no.55 Artem Starodubtsev (UU): Four dimensional topological field theory coupled to point particles

May 23 Grafiti no.125 Abhay Ashtekar (Penn State/UU): Quantum space-times and the issue of information loss

May 25 Quist no.56 Alejandro Perez (Marseille): tba

May 29 Grafiti no.126 Alejandro Perez (Marseille): tba

At least Penn State sometimes puts the PDF of the transparancies online, and the audio,

and Perimeter frequently puts online full streaming video coupled to stills of the blackboard. of interesting seminars in its series.

=====================

I think that Ashtekar may this time consider that some of the information goes into a new fork of time and does not come back out to THIS place as the hole evaporates. this would be a new step and in line with his paper "quantum nature of the big bang".

but we cannot know if Ashtekar takes a new step in the discussion now, because those Utrecht seminars are beyond some damn horizon.

It is obvious what Alejandro Perez will be talking about, and all we will eventually learn is what he CALLS it.

Baez just said in the Baez-Perez thread that Freidel is currently working on THREE papers with Artem Starodubtsev-----this will probably be about a new kind of perturbation expanding 4D spacetime-and-matter around 4D beef.
4D beef is now the non-descript blank nothing, the new tabula rasa or station of departure, instead of Minkowski.

So Renate Loll has Freidel talk on 1 May and then she has Staro talk on 18 May

Hell and damnation.

 

[marcus]

Frustratingly enough, Renate Loll looks to be running the best series of QG seminars in Europe and we don't hear about them or see anything online
...
...
So Renate Loll has Freidel talk on 1 May and then she has Staro talk on 18 May

I forgot to include the link to the seminar schedule
http://www.phys.uu.nl/~loll/Web/seminars/seminars.html

 

[marcus]

happened to come across a listing of Utrecht seminars that gives ABSTRACTS of the talks---so we can see in brief summary what e.g Freidel or Perez was planning to say

http://www1.phys.uu.nl/wwwitf/Seminars/Grafitiabstracts.htm

sample:
A. Perez (Univ. of Marseille, France) - 29 May 2006

Quantization of strings and branes coupled to BF theory

BF theory is a topological theory that can be seen as a natural generalization of 3-dimensional gravity to arbitrary dimensions. Here we show that the coupling to point particles that is natural in three dimensions generalizes in a direct way to BF theory in d dimensions coupled to (d-3)-branes. In the resulting model, the connection is flat except along the membrane world-sheet, where it has a conical singularity whose strength is proportional to the membrane tension. As a step towards canonically quantizing these models, we show that a basis of kinematical states is given by `membrane spin networks', which are spin networks equipped with extra data where their edges end on a brane.

J. Lesgourgues (LAPTH, Annecy, France) - 15 May 2006

Current status of the standard cosmological model

I will review the latest data on cosmological perturbations (CMB anisotropies and Large Scale Structure) and discuss some consequences for theoretical cosmology and particle physics. In
particular, I will summarize current constraints on inflationary models, on the neutrino sector and on the properties of dark matter and dark energy. I will also give a hint of future improvements
expected for cosmological parameter determination.

L. Freidel (ENS-Lyon & Perimeter Institute) - 1 May 2006

Non commutative Effective field theory and quantum gravity

The Coupling of matter fields to spin foam models of quantum gravity will be discussed. We will show in the case of three dimensional gravity how the integration of quantum gravity degrees of freedom coupled to matter can be explicitely described in terms of an effective field theory. This theory is a new non commutative field theory obeying the principle of doubly special relativity. We will also conclude on the extension of this approach to the four dimensional case.