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Experimental Search for Quantum Gravity (schedule of talks)

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Oct27-07, 02:07 PM
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Bee Hossenfelder (who used to post here as "Hossi") has organized a 5-day workshop on XQG. A brief summary with links:

The schedule of talks (5 Nov - 9 Nov) is here

Hossenfelder will give the opening talk and Lee Smolin will give the closing summary
Some remarks on what it was like to put the workshop together (actually a small conference) are in this Backreaction blog entry

John Ellis talk (title "to be announced") is scheduled for Tuesday 6 Nov at 4 PM. Be there or be square. He was one of those who scandalized the nascent XQG community by putting an energy-dependent speed of light spin on MAGIC telescope results back in August. If he avoids this potentially embarrassing topic, or recants, it will surely occasion comment. There has been no followup from the MAGIC group in the intervening months although they have posted many papers on other topics. Maybe John Ellis has some more observational data from the MAGIC collaboration. Or maybe not.

If anyone is there who posts on PF please let us know and relieve the suspense.

So far the best thing about this workshop (or mini-conference) is what Hossenfelder said about it in blog:
Only little more than one week to go to our workshop on 'Experimental Search for Quantum Gravity'. If you recall earlier mentioning of my planning for this event, this is the workshop that originally was titled something with 'phenomenology'. However, in times where people seriously talk about 'qualitative predictions', and 'phenomenology' is turning into a widely abused advertisement slogan, I felt like I had to make really clear what I meant. In addition, 'experimental' is easier to pronounce than 'phenomenological'.

nice thing about Bee is she speaks clearly, oftentimes.
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Oct27-07, 02:17 PM
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Thanks! Great heads-up, Marcus. Can't wait to wade into the streaming videos when they become available. I wonder who is going to be brave enough to talk about MAGIC's single observation of a frequency dependent delay in GRB EM arrival times? Fotini had tagged her hopes on GLAST for such an observation years back, and it would be nice to see GLAST finally launch and observe, so we can see whether the MAGIC result can be replicated.
Oct27-07, 06:53 PM
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Hi Marcus,

Thanks for the link. I am presently about to somewhat un-clutter my life, so maybe there is hope I will have some time left hanging around at PF at some point. The essence of the workshop is essentially what was the point of my talk in Morelia, namely that I think we should try to focus our efforts instead of having several fragmented approaches and people that are politely interested in each other's work, but don't really care about it either. Imo it is a fairly general problem in the community and one that is getting worse: a lack of communication, argument and criticism that in a certain way supports diversity (which is good) but hinders convergence (which is bad). Esp. there seems to be a rather large gap between some of the QG people (many of who strongly tend towards the mathematical side), and particle physics/QFT. This gap indicates a trend I don't like, the community falling apart into more fragments, and therefore my try getting together particle physicists with the QG people. We'll see how they get along.

Regarding Ellis, I have no clue what he'll be talking about. Thanks for reminding me of the MAGIC stuff, I had already forgotten, maybe I should ask him about it.

Besides, one of the nicest features of this Forum are the quotes in people's signatures :-)



PS: btw, not sure if that was you who asked about the initial conditions in Tegmark's MUH, but if so, you might be interested in this (if it wasn't you, sorry, I am really bad with memorizing people's pseudonyms).

Oct27-07, 08:21 PM
P: 271
Experimental Search for Quantum Gravity (schedule of talks)

Quote Quote by hossi View Post
.... tell me about it, even within the maths part of the community. I have heard occassionally that maths is overall more splintered anyways, certainly feels that way to me...
Oct27-07, 10:21 PM
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Quote Quote by hossi View Post
(if it wasn't you, sorry, I am really bad with memorizing people's pseudonyms).
on future visits to your blog, I will be sure to post as Marcus. In this Tegmark case it must have been somebody else, which is fine. You have a lively crowd at your blog and I'd be pleased to be mistaken for almost any of them. Well not absolutely, I draw the line at Uncle Al and Plato.

I see that nobody from the Reuter+Percacci bunch is attending the workshop. One would think they'd be up to cranking out some testable predictions, and would want to talk about it. What fun is asymptotic safety if you can't predict some gammaray dispersion?

When you and f-h say the "maths" side of QG you obviously mean the theory people as opposed to people like Liberati who are concerned with observations. Right now the sense of strife in the theory department is worrisome---there seem to be several battles going on. I realize that this may be a symptom of convergence---the closer to the goal, the more they interfere and step on each others toes.
Oct29-07, 03:34 PM
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I live somewhat near Waterloo and wonder if there would be anything at this conference for the interested ordinary amature? I had so much fun at KITP UCSB's singularities miniprogram last year that I am inclined to try to make this conference. I would email Perimeter directly but they don't list an email address on their visitors information page (
Oct29-07, 04:35 PM
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Why don't you go to Bee's blog? She is one of the organizers. If you describe yourself and your interests briefly and accurately enough she could give you the best counsel about what, if anything, you could do.

My advice would be extremely bad----I have only my gloomy suspicions (not always the best guide).

I think the field of "QG phenomenology" (groping for observable effects which could distinguish the various models and theories and frameworks) or more understandably put: experimental QG is in extremely dreadful shape.
It would, I suspect, drive even brave souls bonkers to listen to a week of XQG talks. In about 18 months I expect it to be different, all changed for the better.

I like and respect Hossenfelder very much----but she and the other 3 organizers cannot achieve miracles overnight.

If I had limited travel resources, then I would be cautious in this case. Think about visiting Perimeter another time, on a different occasion.

But since I totally lack firsthand knowledge, you are welcome and indeed encouraged to disregard my advice.

Here is the blog:
study it so you know who you are dealing with
(there are two authors: Bee is the one at Perimeter)
Oct29-07, 05:12 PM
P: 182
thank you Marcus

It happens that I am planning to pass through that area and it would be pleasent for me to visit such a prestigious institution, despite the raggedy state of QG. Unfortunately it seems the scheduled talk by John Ellis is sold out. It seems there is a general interest in the possibilities for definitive answers from Cern. Still, if I can get the necessary permissions, I am sure it would be worth my time just to sit and watch.

Best regards...
Oct29-07, 10:16 PM
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Whats the old saying: "Mathematicians are like fermions, their brainwaves antisymmetrize, and physicists like bosons, they all coalesce into one'
Oct30-07, 03:07 PM
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Sabine has kindly given me her permission to sit quietly and cause no disturbances. Really, I gave up intentional disturbances long ago, and sitting quietly with a notebook is my habit, so I expect no problem.

Now I am going to be busy reviewing and preparing. I'll check in here more or less hourly if anyone has any comments or pointers for my impromptu visit.
Oct30-07, 03:21 PM
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delighted to hear this! looking forward to any observations you may wish to share with us.
Nov4-07, 02:09 PM
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A very nice drive to Waterloo, with time for sightseeing (not enough time, however) and for reading Dr. S. Hossenfelder’s papers, arXiv:hep-th0702016v2 10 May 2007 Multi-Particle States in Deformed Special Relativity, and arXiv:gr-qc/0612167v2 25 May 2007, Deformed Special Relativity in Position Space, the most recent I could find by Dr. Hossenfelder on arXiv.

I am wondering about the usage, in the 25 May paper, of what I believe to be a neologism, the word “dependend.” I don’t find it in the online OED compact version, and suspect it could be a mere typographical error. It occurs several places, for example on page 2 paragraph 4, “For the following it will be useful to recast the notation in two functions that play the role of an energy dependend speed of light, and an energy dependent Planck’s constant……”

I suppose it could have some special usage that I have missed, since I have not read all Dr. Hossenfelder’s work. I did find and don’t mind typo’s which are not ambiguous, but in this case my understanding of the paper is hindered. Especially since the word is used twice in one sentence, it seems that it should have some significance of which I am unaware.

Really, if anyone wonders, I am not trying to nitpick or be an English minor wise guy. I really am confused and wondering if I have missed something.

It is a pity that the John Ellis talk is listed as sold remaining seats to be reserved. I wonder if there is a rush line?

Nov4-07, 02:47 PM
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The link to Ellis' abstract is mis-directed, but I went to another abstract and got a list, and here is his:

Quote Quote by Ellis abstract
Ellis, John Towards a Phenomenology of Quantum Gravity?

This talk will review proposed tests of ideas about quantum gravity, including searches for quantum decoherence, probes of the possible energy-dependence of the velocity of light, and the nature of vacuum energy. Motivations will be drawn from a non-critical string theory framework.
It appears he will at least address the MAGIC results as one possible test for the interaction of light with space through which it propagates. It's only one result, and there may in fact be a mundane explanation for the 4-minute delay, including morphology and/or dynamics of the source, but if MAGIC can pull off another observation and the frequency-dependent delay is not only replicated, but its duration is found to be proportional to the redshift of the source, papers will be flying. Ellis is highly respected, so it is not surprising that his talk is over-subscribed. I'd like to be there in case he has been keeping something under wraps, though.
Nov4-07, 03:00 PM
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Quote Quote by starkind View Post

Really, if anyone wonders, I am not trying to nitpick or be an English minor wise guy. I really am confused and wondering if I have missed something.
Not to worry, starkind. It is a simple misspelling. There is no current jargon term "dependend" (I am virtually 100 percent sure about this.)
Nov5-07, 07:48 PM
P: 182
A long day, indeed.

Thank you, Marcus, and you are correct. I worked up the courage to ask someone who appears to be close to Dr. Hossenfelder, and she said it is a typo. On that topic, I am rather surprised at the number of typographic errors, and at the places they occur. I guess LQG physicists are too busy to have their work reviewed by someone for grammatical and spelling errors. Or, as is probably the real reason, there is no communication between physicists and lovers of English language. Still, it seems it would behoove one to repair a Powerpoint slide in which the word Comic stands in for the word Cosmic.

Waterloo, for those who may wish to know, is a university town situated among prosperous farms and proud estates behind fenced fields and long gated driveways. It is more southerly than my home in Minnesota, and the trees here still have not entirely shed their leaves.

The fields are wide but not industrial size. Corn and sweet potatoes and beans seem to be the main crops. I see there are several Mennonite churches. My grandfather fell away from the brethren. Still, I am less self-conscious about my full white beard. Probably lots of hardworking farmers hereabouts have them, as is a Mennonite tradition. I even wear black, although some of my clothes are synthetic.

I had planned on camping but there are no campgrounds open nearby. Some tent and trailer parks, but closed for the season. So rich, this land, and so unforgiving to the modest stranger. Luckily I did find a non-hostile parking space not far from P.I. The parking lots charge two dollars an hour, more than I want to pay.

The public library is across the street from P.I., and they have wireless unsecured internet, so I am able to go online in the evening, as now. They close at nine, so I have less than two hours. Less than an hour and a half, now.

A poem:

Marathon Beach

The Lake wants to know
What’s inside every stone.
Pick them up, translucent wet,
And try to see their bones.
They dry, opaque in the hand.
Leave them. The Lake knows
Her treasures. Someday
She will know us all.

Waterloo is not a morning town, but I finally found a Starbucks. The conference started with registration at 0915, and I was up, restless under Orion, at 0400, tortured by thoughts of my insufficiency.

P.I. is a building shaped like a shoebox set on edge. It has a very modernistic random assortment of windows and a black matte finish, with padded flat curved appliqués, reminding me of some futuristic spaceship, Borg perhaps, had the Borg absorbed the creature from the movie, Alien.

I am still innumerate at quantum mathematics, but it is beginning to look familiar. I like the way Dr. Hossenfelder exposes the logic of her maths in her papers. I think I may improve my innumeracy by studying them.

It seems to me that Dr. Hossenfelder is carefully and thoroughly laying foundations for a grand theory of quantum gravity. One of the papers seems to me to verify in terrible detail the seemingly trivial answer to the Soccer Ball Problem, which worries that kicking a soccer ball gives its center of gravity enough energy to cause gravitational collapse. Dr. H. points out that the energy is not really contained in the central point, but is distributed in an energy density field throughout the ball. Not really a new result, but the value of the paper may be in its careful mathematical exposition, verifying and pinning down for all time the otherwise elusive intuitive fact.

They gather in the Black Hole Bistro on the fourth floor, LQG’s up-and-coming along with a scattering of silverbacks. Talking in small groups, drinking free coffee and eating the sliced fruit and muffins. I ask the lady behind the bar if I can buy a cup, and she tells me that the coffee is for anyone. However Dr. Hossenfelder told me not to deplete the refectory supplies, and I would rather bow to her wishes.

Some people look vaguely familiar to me. I think I spot Sundance, tall with long hair tied in back, dressed in a sweatshirt and stylishly faded blue jeans. I get a few quick glances from the participants, but no one lingers long enough to be mistaken for inquisitive as to my identity, or invite an unsolicited conversation.

The physicists are mostly dressed rather casually, with only one middle-eastern gentleman wearing a sports jacket. I don’t see any ties, although several of the older participants look as if they might have one hidden about them, ready to pull out if need should arise. I greatly regret my disability for names and faces. At 0940 the participants begin to drift into the Bob room.

I do recognize Dr. H. from her picture. There have been friendly introductions all around, but I sit alone at a corner table and hope to be mistaken for furniture.

Of course these physicists are shy. No doubt they have all been approached from time to time by crazies who have found the one and only solution to ‘the problem of life the universe and everything’ (Douglas Adams.) Dr. H. gives me a quick once-over, without the slightest hint of welcome. Dr. Einhorn at UCSB was effusive by comparison.

It is time. One last cluster of physicists discuss how data under evolution goes haywire. I wait for them to break, wanting to be last to choose a seat in the auditorium. Two stragglers slow me down, and I do not want to interrupt the proceedings by entering after it has started. As I edge through the door, a student enters after me. I pardon, and he defers. A mature Asian man sitting in the corner smiles for me, and as I bow, my glasses fall off onto the floor. The young man tries to pick them up for me, but I beat him to the floor and get them myself.

The room is not large, but there are plenty of seats. Unfortunately the desks are close together and the physicists have filled all the edges, and the back rows, leaving the center largely empty. I am too shy to bother someone to stand so I can pass, so I go down the steps to the front and sit in the front right corner, at a rather steep angle to the projection screen.

Dr. Hossenfelder begins with a highly competent introduction. She tells the assembly that there is wireless in the building, and they will find a password and user name in their packets. Of course I don’t have a packet. It would be useful to me to be able to consult the web during the talks, but nevertheless I am very pleased just to be there, the fulfillment of a long-time craving

Dr. Hossenfelder says there are still some tickets available for Dr. John Ellis’s public presentation. She says if you don’t have one, to talk to her about it. I am sure she is not including me, and I am far too shy to approach her in person anyway.

Dr. Mavromatos is first to speak. He is the one who had on a sports jacket, but he has removed it now and is in shirtsleeves like everyone else. His talk is called “Quantum De-coherence and Intrinsic CPT violation: towards a smoking gun, experimental evidence in entangled particle states. He starts by pointing out that signals, if they are ever detected, may not be unique to one of the quantum gravity models. And he insists rather strongly that Lorentz violation is not necessarily CPT violation. Then he goes into assumptions underlying various models. Later he says quantum foam is not necessarily made up of microscopic horizons, but may be due to classical particles dipping across the brane, flashing on and off in our detectors.

He says that the press gave more importance to the Magic results than did the Magic researchers themselves. I wish I could remember all the best things he said (Bob Dylan.)

The next talk was by Jack Ng of the University of North Carolina. He is the Asian gentleman who was polite enough not to laugh when my glasses fell off. He apologized for having a touch of laryngitis, and it was very clear that English was not his first language, but I found him mostly easy enough to understand, except the math parts of course. He has all the self-confidence of a POW in Kampuchea, but bravely soldiers on, certain of his work.

He has an idea of how to estimate the amplitude of the quantum foam. It involves a swarm of clocks that correlate to each other. He says his result is in agreement with Gambini and Pullin. He sees the universe as a kind of computational operation. He says the number of ticks in a clock will be a linear function of the mass of the clock. He expects that the Very Large Telescope in Chile may find evidence to falsify his results. Then he goes into the maths. He is insistent that the cumulative factor goes as the cube root of the inverse wavelength, much less than the length per wavelength usually used in calculations. If he is right the VLT should show something. He calculates the amplitude of the quantum foam using the mass of the universe, Hubble’s constant, the possible number of operations (ticks) that have so far occurred in the universe.

There are some severe questions. Dr. M doubts that the numbers are right. It would seem that regular matter should be affected. Others say nucleosynthesis would not occur, that the interferometers wouldn’t work, that the spectra would be different. Someone in the audience points out that the calculations so far are based only on normal matter. Dr. Ng, who has been listening to all this calmly, smiles. Of course Dark Matter and Dark Energy will make the numbers much smaller, bringing them into line with experimental results. Then Dr. Ng goes into an exposition of infinite statistics (as an addition to Bose-Einstein and Fermi) and concludes that Dark Matter particles, if they exist, will have extremely long wavelengths.

Now the library is getting ready to close, and I have only gotten to the first two talks. I wish you had been there, I am sure you would have been more observant and knowledgeable. My goal here is really to hear and see the language of physics spoken in its natural environment, and I am very pleased to be able to listen in. I only wish I had been in this company from the age of 12, when I first began to think of what could lie at the ends of the universe.

Best regards, more later,

Nov5-07, 07:59 PM
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Thank you for the blow-by-blow!!
Nov5-07, 09:26 PM
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Yes, thanks!
I like your writing, Starchild. It's distinctive and it's nice to have the extra visual and experiential detail.
No need to be in awe of those PI people despite all the brash selfconfidence and/or prominent reputations. I could be wrong but I'd guess that some of them are probably feeling quite awkward and nervous themselves.

I HOPE I'm wrong, but I still have the impression I told you before, that the field of XQG is in a dreadful mess and is almost a non-field.

Sabine has taken on the assignment to jump-start it, and I believe she is new at organizing conferences------what you are seeing could be like her first ever workshop. Eventually it is all going to work----XQG will be a wondrous burgeoning specialty, SH will be recognized as highly capable leader in it etc etc---but at the moment my feeling is it's iffy.
Nov6-07, 05:48 AM
P: 344
Dear starkind,

Thank you very much for your report. Your writing reveals the sensitiveness of a wise and modest person, and I appreciate to learn about that workshop from you. Please continue if you have time to.

Kind regards,

PS- You wrote: "I only wish I had been in this company from the age of 12, when I first began to think of what could lie at the ends of the universe." I feel like I have missed the time and the place to be where those people are now. But I have been more enthusiastic in previous times. I feel more and more skeptic now, and trying to regain my contemplative mood about Nature. LQG is evolving, but at the same time, it is getting more and more confusing, IMHO. It is an active field, but I'm not certain at the present time about what will come out of it. Instead of getting more enthusiastic, I'm getting more skeptic. I firmly believe we need an ontologic revolution to get a correct quantum theory of gravity. That is where my mind and energy are heading now. But I appreaciate to keep in touch with what is going on. Thanks.

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