Experimental Search for Quantum Gravity (schedule of talks)

[marcus]

Bee Hossenfelder (who used to post here as "Hossi") has organized a 5-day workshop on XQG. A brief summary with links:
http://www.perimeterinstitute.ca/esqg07/

The schedule of talks (5 Nov - 9 Nov) is here
http://www.perimeterinstitute.ca/en/Events/Experimental_Search_for_Quantum_Gravity/Schedule/

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
http://backreaction.blogspot.com/2007/10/experimental-search-for-quantum-gravity.html

EDIT:
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.

 

[turbo]

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.

 

[hossi]

Thanks

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 :-)



B.

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).

 

[f-h]

fragmentation

... 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...

 

[marcus]

(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.

 

[starkind]

Hi

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 (http://www.perimeterinstitute.ca/en/About/General/Contacting_PI_and_Directions/ )

 

[marcus]

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
http://backreaction.blogspot.com/
(there are two authors: Bee is the one at Perimeter)

 

[starkind]

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...

 

[Haelfix]

Whats the old saying: "Mathematicians are like fermions, their brainwaves antisymmetrize, and physicists like bosons, they all coalesce into one'

 

[starkind]

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.

 

[marcus]

delighted to hear this! looking forward to any observations you may wish to share with us.

 

[starkind]

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 out...no remaining seats to be reserved. I wonder if there is a rush line?

Thanks

 

[turbo]

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

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.

 

[marcus]

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.)

 

[starkind]

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.

more later,

S.

 

[turbo]

Thank you for the blow-by-blow!

 

[marcus]

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.

 

[ccdantas]

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,
Christine

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.

 

[marcus]

...LQG is evolving, but at the same time, it is getting more and more confusing, IMHO...

Christine, I sketched a "map" or outline of currently visible QG work, in this other thread
https://www.physicsforums.com/showthread.php?p=1493719#post1493719

It is just my own current map but it might help.
Here's an alternative link, if that one doesn't work.
https://www.physicsforums.com/showpost.php?p=1493719&postcount=3

My feeling is that if you look at the whole picture, background independent QG is converging and getting clearer.
So the growing sense of confusion may result from the fact that we see more and more people all the time, with more and more ostensibly different approaches.

What feels like confusion might be a result of population growth, rather than something intrinsic to the research itself.

XQG is a different kettle of fish. They are still trying to mix string and non-string phenomenology, which I don't think works.

You may disagree. Have a look at my map and see what you think.

 

[starkind]

A long day at P.I. part two

thanks to all for the kind comments and support.
S.

0711060755 Waterloo, Starbucks on King street.

The next talk was by Jess Niemeyer, of the University for Theoretical Physics and Astrophysics, Wurtzburg Germany. He talks on perturbations giving rise to the Cosmic Microwave Background, beginning with an assertion, stated rather forcefully, that the Bunch-Davies is the unique adiabatic vacuum. After some vigorous objections and questioning, the point is ceded so that he can continue his presentation. His best defense seemed to be that the assertion is necessary, but not a sufficient condition to the argument.

Someone, Dr. Mavromatos, I think, asked him why he is starting out by violating Lorentz invariance. He pauses for a heartbeat, just long enough for a quick mind to wait for it, and says “Oh, just because everyone else is.” This draws perhaps the best laugh of the day.

I understand very little of his mathematics. He did say at one point that the brane contains observables, and the bulk does not, which seemed familiar to me. Much attention is given to light cones and modifications for inflation, which result in some events which are in the light cone at early times to leave the light cone later, and then still later, return to the light cone. Of course it really isn’t a cone in this model, since light cone assumes constant speed of light.

At some point in the discussion, Dr. Mavromatos, who throughout the day was garrulous and liberal in gesticulation, diverted the discussion for a moment into something having to do with “D” particles, which occur as defects in the bulk. This idea caused me to perk up a bit, since early on in my studies I thought that matter in general must be a sort of defect in a crystalline background structure. Later I tabled this notion since the arguments on PF seemed to be insisting on background independence

Is it possible a sort of background may yet exist? Dr. Ng’s analysis seemed to me to include a physical “clock” mass field, in which he said individual clocks would be separated by an interval equal to the Planck length. Fundamentally, each “tick” would correspond to a single timelike basis unit.

Dr. Mavromatos seemed to be leading the critical but friendly sorties from the gallery. Often his questions led to interesting discussions, and I noticed that several elders had joined this session, including a gentleman who spoke a good deal, and who I thought looked something like the pictures I have seen of John Ellis. Of course I am not to be relied upon on this identification, since my disability in names and faces is trumped only by my quantum maths innumeracy. Again, I wished I had a program guide to the players.

At 1600, after a coffee break which I spent exercising by climbing four flights of stairs to loosen up any blood clots that may have formed in my legs, Dr. Daniel Sudarsky gave a talk on the quantum origin of the cosmological structure. Perhaps I was getting tired, but I am afraid I followed very little of his talk. I have only noted that his talk began with a discussion of the shortcomings of standard lore (in cosmology), continued with the need for an extra element tied to QG, and ended with a discussion of possible tests and predictions.

At 1800 Dr. Matt Visser, who has worked at Victoria University in New Zealand, but who now is associated with P.I., if memory serves, gave a very energetic and motivational talk on Emergent Dispersal Relations and their lessons for QG. Dr. Visser is an entertaining speaker and knows how to use expectation and delay to keep his audience interested.

Much of his talk had to do with the condensed matter analog model program and emergent analog spacetimes. He gave a rather speculative analysis which led to the conclusion that the square of frequency is a function of a tensor involving only h-bar with a raised index i, and a K with a lower index in i, squared by another K with index j.

I was captivated, but handicapped by unfamiliarity with several of the terms, and only a fleeting acquaintance with condensed matter. Some of the terms I was not sure of: “Rainbow spacetimes,” “acoustic spacetime,” “rainbow metric,” “conformal factor,” “threshold corrections,” and the Bogoliubov dispersion relation.

I am sure the cognoscenti are laughing at my ignorance. Again, I would have liked to be internet connected so as to reference Wiki and other sources.

There were many side discussions in the question period, and I believe it was Dr. Mavromatos who asserted his suspicion that gravity is an emergent phenomena, not an underlying one.

Dr. Visser ended his presentation with a quote from Einstein, “it is important to keep an open mind, just not so open that your brains fall out.” As I recall, Dr. Einstein was speaking of his doubt of the validity of quantum mechanics.

At 1900 there was a talk by Silke Weinfurtner, who several times deferred to Dr. Visser, and gave a very informative talk on the mass generating mechanism for Nambu-Goldstein bosons in emergent spacetime and its application for QG phenomenology. Much of this talk was a description of ongoing experiments in condensed matter. I learned a lot about this interesting area, but probably only because my ignorance is so abysmal. The things I learned were very general and probably would not be of interest here.

There was much discussion of the relevance of analog models to reality, and several times Dr. Weinfurtner had to appeal to the defense that her presentation was of a toy model, and the results were not exact, but interesting because several of the other models, for instance the electromagnetic waveguide models, have led to very similar results.

After the talks ended, there were the customary clusters of interest groups discussing topics in the hallways. I filtered through them to the elevator, where two participants got on for a mostly silent ride down to the lobby. One of the doctors commented that it had been a long day. It seemed that I was expected to say something. “And again, tomorrow,” I commented. This meaningless vocalization was enough to break the social territorial tension, and might have admitted me to their further discussion in the lobby, but I was anxious to get my experience down to digits while memory was still fresh.

Before I left, I was honored by some attention from the woman who seemed to be close to Dr. Hossenfelder, and she told me I had an office for my use, which initially surprised me greatly. She told me that I should pick up my packet at the registration desk, and I might have taken this opening as a means to gain access to privileges, by misrepresenting myself as one of the absent invitees. As much as this would have been to my immediate advantage, I declined, telling her my actual name and position, or rather, lack of a position. “My presence here is unofficial,” I said. She seemed somewhat abashed and probably had mistaken me for someone else, or else was embarrassed by my un-clever refusal to take this proffered opportunity.

Today the sessions begin at ten, and I have almost two hours to prepare. I will go to the P.I. and try to take advantage of whatever public facilities may be available. Maybe I can score a seat at the Ellis presentation. I hope so.

S.

 

[marcus]

...As much as this would have been to my immediate advantage, I declined, telling her my actual name and position, or rather, lack of a position. “My presence here is unofficial,” I said. She seemed somewhat abashed ...

Starkind, whatever it takes for you to observe and write clearly from your particular viewpoint. But this is eeyoring it with a vengeance. Wilt sleep on thistles, when angels offer thee a feather bed? Still, bravo on your reporting. I, and I expect others here, eagerly await more.

 

[ccdantas]

Very well Starkind, and I hope you can attend Ellis presentation.
Best wishes,
Christine

 

[ccdantas]

Christine, I sketched a "map" or outline of currently visible QG work, in this other thread
https://www.physicsforums.com/showthread.php?p=1493719#post1493719

It is just my own current map but it might help.

Thank you Marcus, it does help.


Christine

 

[starkind]

Noon break.

I think the "woman" of the previous post is probably Dr. Dittrich. I have been fortunate enough to obtain a username and password, so I can report, and research, more freely. Her picture on the post-doc page is somewhat dated.

http://www.perimeterinstitute.ca/in...h &f=3&name=Bianca Dittrich &resident_id=1236

I must say if it is indeed a correct identification, that she looks much better than her photo.

As for thistles, Marcus, you have no idea. Life has always been uncomfortable for me, by my own alienation. No ones fault, just the way it is.

Dr. Sudarsky is the chair of today's sessions. There is hope that I may yet get into Dr. Ellis' talk. I have found out that there is indeed a rush line, and I am privileged to wait at the end of it.

Today’s first talk was by Dr. Hinterleitner on DSR and Classical Gravity, a broad overview. He started with outlines of the approaches to QG, and then talked about the implied drastic changes to the mathematics at the Planck scale. LQG gives a discrete spectrum of geometric quantifiables with an invariant length, as in the ultraviolet cut-off. The question is if LQG is compatible with SR.

Does LQG distinguish a preferred reference frame, or is it possible to conciliate the existence of an invariant length with the principle of relativity? Dr. Hinterleitner concludes that the latter is the correct view. Relativistic theories with an invariant quantity in addition to c are called Doubly Special Relativity, or Deformed Special Relativity, as may be the more descriptive term.

Dr. Hinterleitner also introduced Hopf algebras as the only applicable mathematics, and discussed DSR in momentum space, dispersion relations, DSR in spacetime, Formulation in de Sitter space, Velocities, and other modifications. Then he talked about DSR and gravity, Classical gravity, LQG and QFT in curved space, and discreteness and Lorentz invariance. His talk was mostly mathematics and I followed only a little of it.

Dr. Mavromatos resumed his position at the head of the sorties, and asked if DSR is induced by an energy dependent metric, is it fundamental or effective. Dr. Hinterleitner was taken back a little by this and took some time to respond, and he used the defense that this is only a toy model. Dr. Hinterleitner agrees that it should be considered effective, and Dr. M is satisfied and withdraws his question.

There was some discussion of the rainbow metric. Each object in ST has a different metric. Where the gravitational fields are weak, the metrics are flat, but there are infinitely many local states. The spectral collection of metrics is called the rainbow metric.

There was much mathematics again, but it all seemed to lead up to the idea that if the speed of light is infinite ( I guess if it is variable it could be made infinite?) then the limiting speed of massive particles is also infinite, since the limiting speed of massive particles is equal to c in all DSR versions.

Dr. Visser wondered if this means that DSR is really broken SR, since SR requires that particles cannot travel at light speed.

Hopf variables provide stricxt rules governing definitions of algebraic relations with deformations of co-product. It is an algebra equivalent to the geometric construction of de Sitter space.

Dr. Hinterleitner ended with a diagram of the relationships he had described. It shows that LQG leads to discreteness which leads to modified dispersion relations, which can lead either to variable constants, or to DSR as a curved momentum space. Hopf algebras then describe a non-commutative DSR spacetime.

The next talk was by Dr. Girelli from SISSA in Trieste Italy. He is in collaboration with Dr. Pullin and will discuss findings of the paper, gr-cq/0710.4393. The over-riding need is for a theory to connect experiments which are soon to be performed (I suppose at Cern, Ligo, etc.) He takes a liberal point of view in relation to strings and “D” particles, a statement which drew some laughter. I gather that Dr. Girelli is considered more radical than liberal by the audience.

Dr. Girelli points out that DSR can be done in three dimensions and cites Friedel-Levine. Four dimensions can’t be done, yet, except in models where large parts are put in by hand, as effective field theories. DSR is not just special relativity with strange coordinates, but is really a modified SR. For example, he cites theories with a bi-cross-product basis, best defined in 5d space where momentum space is curved.

QFT on k-Minkowski space raises physical questions. What does it mean that the sums of momentums are non-commutative? What is the solution to the soccer ball problem? What is the physical meaning of the operator Pi, (not the geometric Pi, relating circumference to radius……or is it, I wonder?)

Another angle of attack on the problem is the idea of a modified reference frame.

Dr. Smolin has been participating in this discussion, but I am not fast enough to record the gist of his questions.

Dr. Girelli finishes up by saying that the rainbow metric is the same as the Finsler metric, which he will be talking about on Saturday. The Effective frame of reference becomes momentum dependent. Similar results are obtained by renormalization group approach. However it is still not clear how this exztends in the multi-particle case.

This presentation stimulated many side discussions which I was not able to follow, much less record. The above summary is rather disjointed, since I don’t seem to be able to listen and write at the same time. The conversations get ahead of me. Dr. Sudarsky asked that these side discussions be held at a later time.

So, is symmetry broken, by a preferred reference frame, untouched as in the usual interpretation, or deformed by modifications?

Dr. Girelli suggests that the quantum reference frame is fuzzy. What is the precision of QRF? How robust is it? These results may have to trade off (I am reminded of the uncertainty of energy and position in Heisenburg.) He concludes that QRF is essential in all QG approaches in the construction of some observables. This approach is also of interest to Quantum Information Theory researchers. The aim is to construct a QRF using QFT.

Dr. Smolin commented that this approach is beautiful, but that he was confused about the QRF having different dispersion relations.

And so the break for lunch. now it is time for Dr. landsburt to speak about Out-of-this-world-Physics, probing quantum gravity in the laboratory.

More later,

S

 

[garrett]

Hey starkind, thanks for PF blogging the conference, your reports have been very entertaining.

If anyone would like to see some pictures too, I was at PI a few weeks ago:

http://sifter.org/~aglisi/albums/Perimeter07/

 

[starkind]

Great pics, Turbo. I see it was warmer when you were here. We had snow today. I would post some pics if I could get time and energy to download the full chip in my camera. I am a little tired after another day of intense concentration, but in a happy way. If Canada would let me, I would try to stay here forever. However, there are other places to visit. Columbia, Penn State, North Carolina, Ole Miss. And, some of them are warmer!

It turns out I do look a bit like John Ellis. He is thinner, more elegant, but we both have rather long gray hair and full gray beards. I have also been mistaked for someone named Tom. Dr. Ng addressed me as Tom today. He quickly realized his error, but I did get a couple questions in about clocks. He says he thinks the best choice would be black holes. I wondered what the universe would look like if it were filled with miniature black holes at a spaceing of one Planck?

I also asked him if he imagined his clocks in a lattice arrangement. It seems he has not considered this. I wondered if there were flaws in the lattice, what would that mean for spacetime? He was not prepared to discuss a universe where mini-black holes pop in and out of the brane in a virtual way, and the thing we call matter is a flaw in the pattern. It is an old dream of mine, and until I know the maths, I cannot develop it. Dr. Ng did not seem to think much of many worlds theories either.

People in general were more freindly today. Perhaps they mistook me for Dr. Ellis, or perhaps they are getting used to seeing me lurking about in the corners.

I am tired, but will try to summarize the afternoon events offline.

Thanks

S

 

[starkind]

0711061930 Bob room, P.I.

Snow! Maybe it is a sign that there will be some no-shows to Dr. Ellis’ talk tomorrow, and I’ll get in. I did work up nerve to talk to Dr. Hossenfelder, and ask her if she could get me a ticket. She said to ask the concierge, but didn’t seem too hopeful. I mentioned that I was writing for PF, and that people here were especially curious about Dr. Ellis’ presentation. That seemed to carry some weight and she said she would see what she could do.

Dr. Lundstrom says that it will be as much as seven or eight years before we have any results from LHC. And we have already waited so long! He says every time he visits the website, they put back the end of commissioning. There is a lot of calibration runs to do, and the workers have to learn the tricks of their marvelous beast.

John Ellis gave a talk at 1615, toward a phenomenology of QG. He has been working on what he calls a non-critical string approach. He almost apologized to the assembly, and nodded to Dr. Smolin, but said string is still the most complete theory.

His talk went along lines that have by now become familiar. Modification of the Lorentz invariance. High energy atmospheric gamma ray bursts. Active Galactic Nuclei and the dependence of light speed on energy. Violation of the equivalence principle. He sees particles traveling at c as a violation of equivalence, but does not explain his thought on this, only nods again to the fact that it is not the usual interpretation of EP. Anyway it is not the topic today. His current work is applicable only to photons, and has application to Inflation and Dark Energy, to which he says he has a different approach.

He is also concerned with gravity growing in proportion to E. Something about the two graviton exchange being infinite. Gravity being non-renormalizable. Pure states evolving to mixed states. He has issues with all these ideas.

He describes the nature of the quantum vacuum as a fluctuation in the fabric of space-time. Changes in energy, space-time topology, time and delta xi (I didn’t catch what that was) are all very close to an order of one. He refers to Wheeler’s image, quantum foam.

Are there testable observable manifestations of quantum foam? Can it be neglected? He says he hopes not.

He calls the addition of GR and QM the unfinished business of 20th century physics, and the first task of the 21st. One or the other or both must be modified. Some approaches are a modification of QM, violation of Lorentz invariance, breakdown of the equivalence principle based on astrophysical data. And, the search for a distinctive signature not allowed in QFT.

String is mainly working in the context of point-like particles as extended objects. In the simplest case there is not divergence in perturbation theory. Quantum consistency fixes the number of dimensions, bosonic string theory having 26 dimensions, superstring theory having ten. There are non-perturbative configurations involving D-branes. Black hole entropy is equivalent to the number of D-brane states. He wonders if this is the whole story?

And is QM to be modified? Here he says his talk overlaps that of Dr. Mavromatos, and he skips through it. The concerns are macro Black Hole mixed states involving thermodynamics, temperature, entropy, loss of information. Can a mixed state evolve from a pure state? Sic transit QM, or anyway our naïve version of QM. Also at the micro BH level. Sum over foamy configurations and loss of information in the foam. Asymptotic scattering described by transitions between in states and out states. Baryon number not conserved at the Planck scale. B not an exact gauge symmetry means no B hair. Proton decay via virtual BH involving a dimension 6 operator.

In superstring theory, is QM modified at the BH horizon? Will non-QM effects occur?

A lot of stuff I didn’t understand about a non-trivial “dollar” matrix which entails CPT violation, reference to Page and Wold.

He is interested in application to neutral kaon systems, a two state Hamiltonian, k_1 k_2 basis.

I am pretty lost here. I missed much of what he said, and the above may be reduced to mere gibberish, but perhaps someone will know more about these things than I do.

Then he talked about probes of QM using CPLEAR data on k to 2Pi and k to Pi eV decays. QM agrees with experiment at sensitivity of 10-2 GV, pretty good, he says, one part in 10-20 in neutral kaon.

He has slides on QFT on the world sheet, something about obstruction of elevation to space-time, problems with BH physics, violation of Lorentz invariance due to recoil of background on energetic particles.

Another slide on modification of Lorentz invariance. We must be crazy, says Dr. Ellis, and shrugs his shoulders and goes on. Space-time foam as a non-trivial medium, large fluctuations at small scales, back reaction to energetic particles, non-trivial refraction index, effect on propagation that increases with energy. He says the non-critical string theory has a xi operator equal to minus one, as needed to avoid Cherenkov radiation in vacuo.

There was a question about composite particles and the soccer ball effect, for example, quarks in a proton. Dr. Ellis washed this off with the comment that his non-critical string theory only deals with photons, so there is no soccer ball problem.

Non-critical string theory has energetic particles propagating through a foam of D0 particles. They interact so that the D0 particles recoil, a motion which modifies the flat space-time metric, where U_i proportional to the energy divided by the Planck mass is the recoil velocity. Hence the modified Maxwell equations, which I did not have time to copy. He also showed the modified dispersion relation, k square minus omega square minus two bar-omega k omega equals zero, and a formula for subliminal propagation. He said he thinks we need to revisit the idea of phase space.

In Astrophysics, there are problems with Lorentz violation. The time delay from a distant object proportional to energy. We need to look for objects with fine time patterns, small intrinsic delta-t, such as high energy gamma ray bursts and active galactic nuclei. He shows an updated analysis including HETE data, ref his paper astro-ph 0510172, with Mavromatos, Nanopolis, Srednicki and Sarkisyan.

Are there source effects that may muddy the propagation effects? Problem avoided by evidence for stochastic spread in intrinsic delays at source. Multiple sources are needed and statistic techniques to deal with them. And we need a better understanding of the physics of gamma ray bursts.

Then he went into an exposition of new analysis of flaring AGNs, namely Markarian 501, with a red shift of z=.034, July 9 2005, which had a short rise-fall time. On this event a possible 4 minute delay was reported. He complained that the result was trumpeted about on the blogosphere without noting that the researchers stated that it looked like a shift but they could not be absolutely sure. The significance of the time delay was calculated at less than 95 percent, which leaves a five percent chance that the time delay was due to effects at the source.

Then he went on to talk about other AGNs, e.g. HESS multiple flare with a large red shift providing more data.

After this he switched to a discussion of the violation of the equivalence principle. Dr. Smolin pointed out that his data didn’t account for a leading term dimension 5 operator which gives a parity breaking effect, such that one polarization is faster and the other slower, which disagrees with the model. The model predicts all photons are faster. Dr. Smolin said something about the distinction between breaking and deforming is whether parity is even or odd.

Dr. Ellis countered that he expected the parity to be even. Dr. Mavromatos interjected that they were ruining his talk, which drew a refreshing laughter from the audience. Dr. Ellis pointed out that when parity is odd the suppression (?) is many orders of magnitude larger, but it doesn’t matter, because the test only considers even parity.

Then Dr. Ellis went on to discuss synchrotron radiation constraints from the Crab Nebula observations. Then he mentioned non universality in the D-brane model, which Dr. Mavromatos also discussed in his talk. He said his non-critical string approach describes inflation, agrees with the Hubble expansion, and shows how motion of the D-branes could provide the energy driving the inflation.

Then he discussed dark energy, and called it a challenge for string theory. He said something about it having a negative energy component, but I missed it.

Dr. Ellis concluded that only heuristic discussion is yet possible. His non-critical string theory is one proposal.

At 1730 Dr. Marco Cavaglia gave a talk on the phenomenology of black holes in particle colliders and cosmic ray showers. But it is now 2100 by my watch, and I am too tired to finish this tonight.

More tomorrow.

S

 

[ccdantas]

Hey starkind, thanks for PF blogging the conference, your reports have been very entertaining.

If anyone would like to see some pictures too, I was at PI a few weeks ago:

http://sifter.org/~aglisi/albums/Perimeter07/

Great photos Garrett!

And good job Starkind!

 

[starkind]

I am becoming dazed by trying to write notes and keep up with lecture pace. Then, there is the problem of having time to write the reports during lunch break, before opening, and after the close of the day.

So, I will beg off submitting full descriptions for now, and only attempt easy summaries. This is lots of fun, but exhausting.

S.

 

[starkind]

Dr. Stephano Liberati talked about new constraints on Planck scale Lorentz violation in QED from Crab Nebula today at 1000 hrs. Then Dr. Claus Lamerzahl from ZARM at Bremen University, GDR, summarized possible stratagies for the search for quantum gravity induced effects.

Dr. Liberati’s talk asserted his belief that it will be possible to test QG. He believes that Lorentz violations will provide the first glimpses. His talk focused on Effective Field Theory and Lorentz violation, with theories using either renormalization or higher dimensions, leading to EFT with Lorentz Invariance Violations (HE LIV) or QED with dimension 5 operators. Reference Myers and Pospelov, 2003.

He commented on the astrophysical constraints in time of flight experiments, the best of which currently is MAGIC using Markarian 501 flares with a xi value less than 47. However there is no LIV evidence so far.

He said EFT removes the problem of source effects.

His presentation included a delightful time loop image of the Crab Nebula in optical and radio frequencies, showing the pulsar, its energy beam, and the surrounding radiation effects.

He stated that EFT doesn’t work for quantum gravity. Dr. Smolin asked it this statement included DSR. Dr. Liberati said that DSR has weird effects, but may allow EFT.

He concluded that it is interesting to keep looking for time delay, and if a signal is found it would put QG on a different track from EFT. He is waiting on results from GLAST.


Dr. Lammerzahl provided perhaps the clearest summary yet of the state of QG. His power point presentation was very well-organized, being flawed only by a choice of colors in some items which did not show up well on the projection screen. He announced the first production of a BEC in microgravity which occurred yesterday 6 Nov 07 at the drop tower at Bremen University (see my new thread, news from P.I.)

Dr. Lammerzahl said that the Finsler metric would be difficult to obtain. Dr. Visser objected, said it had already been done, citing bi-refringant crystals.

Now there is just time for me to go eat my carrots. More later.

S

 

[starkind]

0711061415

I see that I hastily skipped over my notes on the talk by Dr. Landsberg, who spoke on the sixth.

His talk was very interesting for me, because I have long been curious about lab results from colliders. Often conclusions are presented without the actual data, which is in the form of abstract images anyway. Still, I have been fascinated by cloud chamber results, and have wanted to understand the significance of the occasional collision image presented in the general press. Unfortunately, this meant I was often trying to see the slides, not copying notes.

Anyway, Dr. Landsberg, from Brown University, talked about the hierarchy problem, models with extra dimensions, gravity at short distances, astrophysical constraints, collider search for extra dimensions, and the observation of BH at future collider events.

Dr. Landsberg started by pointing out that large hierarchies tend to collapse. He gave humorous examples from competitive social human tower events and political realities. However, he said, there is no physical reason why these collapses have to occur. He said fine tuning does occur in nature, which acts to keep some natural large hierarchies stable. His example was the lunar eclipse of the sun, with its unlikely coincidence that the optical angle of the moon matches the optical angle of the sun nearly exactly. He also pointed to the astounding results of the Florida recount, in which the proportion of votes for one party to the other was 1.000061. I did not ask him if he thought this was a reasonable coincidence, or an impossible result.

The alternative explanation, he said, is the anthropic principle, which, in Missouri, is referred to as intelligent design. This part of his talk was, of course, motivational, and raised the mood of the room considerably.

He then talked about constraints on the size of large dimensions from small distance gravity experiments, which restrict the size of large dimensions to less than about 1mm to 1fm. He mentioned that bulk space is a large extra dimensions idea.

Then he discussed the 1999 Randall-Sundstrom model. He said that in the one plus brane, there are no low energy effects. In the two plus brain and 1TeV Kaluza-Klein modes of gravitation there are low energy effects on small brane, and hierarchy problem is solved naturally.

The best current measure of g at short distances is University of Washington torsion balance experiments, a high-tech remake of the 1798 Cavendish experiments. U. Washington has shown no effects down to r=.16 mm. New ideas include atomic interferometer for precision measurement of acceleration, and evidence from monojets.

At this point there were some pictures of collisions, which have been a long time point of curiosity for me, and my notes end.

However, from my memory, he showed what a BH signature would look like. Its main distinction is that the radiation would be very spherical, due to the fact that the BH is very democratic, and can produce any kind of quanta at all, at any angles. He showed some graphs of data showing the spherical radiations. He also said that the signature of a BH would be very energetic, and would show some energy losses due to gravitons leaving the brane.

 

[ccdantas]

I see now that the talks were posted:

http://www.perimeterinstitute.ca/Events/Experimental_Search_for_Quantum_Gravity/View_Experimental_Lectures/

 

[starkind]

Just checking back quickly to report that Dr. Hossenfelder did turn up with tickets to tonights public lecture, and she was very pleasent about it. She actually smiled at me, and I was thrilled. There are cabs leaving from PI in about twenty minutes, and I am sitting in the lobby with Dr. Ng, who also was on the ticket and cab list.

 

[starkind]

Dear starkind,

...I feel more and more skeptic now, and trying to regain my contemplative mood about Nature. ...

...I firmly believe we need an ontologic revolution to get a correct quantum theory of gravity. ...

Christine

Thank you for the personal tone of your note. It happens that a contemplative mood about Nature is one of my priorities too, and always has been, as far back as I can remember. It has often been the case that human activities have driven me to seek consolation in that which humans have not touched.

I also agree with the need for an ontological revolution. As you may recall, the KAVLI mini-program last January on singularities ended with a statement by the organizer that what is needed is a new interpretation of time. That would surely achieve a revolution in concept, if not in physics itself. But we are so deeply committed to our view of 3d space and 1 or 2d time that it seems almost impossible.

It seems that the idea of time is also on the minds of others here. A questioner in the audience last night at Dr. Ellis' public talk asked about the true nature of time and space, and this set off a lively discussion afterwards between Dr. Hossenfelder and Dr. Mavromatos, which lasted until the room cleared enough for us to make our way out to the lobby. Dr. Mavromatos asserted that time is more fundamental than space, since how could anything happen without time? Dr. Hossenfelder seemed to me to take the opposite point of view, one which I myself encapsulated years ago in a little rhyme:

"I can imagine an unmoving place, devoid of dance,
but what movement could take place
in time devoid of circumstance?"

There is understandably a great reluctance to assign a privileged position to time or to space, and Dr. Einstein sets them as equivalent. Almost all of our physics can be reduced to units of space and time, perhaps supplemented by mass or charge. A new view of time and space would almost certainly kick one of the legs out from under our most cherished basis! Everything we think we know would be affected.

It is likely that my understanding of Dr. Ng's work is inadequate, yet it is certainly evocative that he quantizes time and space by assuming space is filled with clocks ticking at a Planck time, due to their proximity and interaction with each other at a Planck length. Perhaps a view of this kind, going at the problem directly from time and space, will in the end provide a more powerful model than that we have had so far, starting from apples and cannon balls and working down to atoms and quarks.

Perhaps Dr. Ng will get his Noble prize after all, and join in the honor already won by his academic cousins, brothers, father and grandfather. Dr. Ng was a student of Richard Feynman.

His most recent paper on arXiv is found here: http://arxiv.org/PS_cache/gr-qc/pdf/0703/0703096v2.pdf

 

[starkind]

Dr. Ellis’ public presentation to the Waterloo, Ontario population last night was very smooth and aided by high caliber professional power point projection. It was evidently his standard talk, which he has doubtless given hundreds of times by now. While the pictures of the CERN Large Hadron Collider project were beautiful and very informative, little or no new information came out of the talk.

The CERN LHC project is supported by countries from all over the world. The U. S. and Canada were two among many who have provided material and technical support. This talk was given to a Canadian audience and so was slightly tailored to please them by emphasis on Canadian contributions.

The new information came after the talk, during the question and answer period, in which members of the audience had an opportunity to speak via microphone to the room. Dr. Ellis was asked about “the magnet problem last summer,” to which he replied, “Which one?”

Of course the big magnet event was an unforeseen rapid expansion of magnets used to focus the beam into a width thinner than a human hair. To give some idea of the intensity of this beam, it is calculated at full operation values to carry the energy of a fast freight train. Imagine a freight train at full speed crammed suddenly into the width of a human hair and you have some idea of the immense forces involved. The resulting expansion was reported in the popular press as an explosion, a word which Dr. Ellis objected to on the grounds that it did not involve kinetic energy from a chemical reaction. He said one Madrid paper went so far as to say that the entire city of Geneva had been destroyed, but Dr. Ellis assured us that in fact Geneva is still there.

All the damage has been repaired, and the commissioning of the giant machine, which circles twenty seven kilometers long beneath Switzerland and France, continues. Dr. Ellis said that despite continuing discovery of minor problems requiring fix-it time, the huge accelerator will come on line next year and can be expected to produce its first data sometime before the end of 2008.

This machine will produce collision events between protons with an energy of one TeV, enough so that scientists suspect that miniature black holes will be produced at a rate between one per minute to one every ten minutes. These miniature black holes will evaporate in a millionth of a second, and so they pose no danger of swinging back and forth through the center of the Earth and eating up the ground we stand on.

As further evidence of the harmless nature of these mini-black holes, Dr. Ellis pointed out that high energy cosmic rays a hundred times stronger than the LHC have been slamming into the earth’s atmosphere from the beginning, and yet no one has reported any reduction in the earth’s volume. Evidently even if a mini-black hole is discovered in the collisions, it will not cause anyone any reason for anxiety.

The talk was very general, of course, and aimed at encouraging continuing support for large scientific projects of this kind, which have spin-off value in the field of medicine, as well as inspiring other new and useful technology. For example, the World Wide Web was developed to allow scientists across the world to contribute to this effort without actually having to commute.

The results of this device will have an effect on many areas of physics, from cosmology to string theory to quantum gravitation and the search for a grand unification of the four physical forces. We have a lot to look forward to in the next few years, and everyone involved is optimistic that it will be worth the wait, and the expense.