Strings 2005, the latest in a series of yearly huge string theory conferences, will be taking place this week in Toronto. This series began in 1997 in Amsterdam, and in recent years has attracted 445 participants to Cambridge in 2002, 392 to Kyoto in 2003 and 477 to Paris last year. So far there are about 415 people already signed up, so it looks like this year’s conference should be similar in size to ones of the last few years.

I expect that some string theory bloggers wil be reporting from the conference. In particular Jacques Distler will be there, chairing a session that should include two of the loonier talks of the conference (Kachru and Douglas on the landscape), and presumably we’ll be hearing from him. Last year there were several people reading “Not Even Wrong” on their laptops using the wireless connection in the lecture hall in Paris, this year I hope anyone there who doesn’t have his or her own weblog will let us know what is going on by posting comments here.

The conference will end next Saturday with a public lecture by Lenny Susskind. His talk has the same title as his forthcoming book on the landscape pseudo-science. The theme of the public lectures is listed as: “If String Theory’s the Answer, What’s the Question?”

**Update:** Slides from the conference have already started to appear, including Ooguri’s survey talk on topological string theory, one of the few subjects in string theory which seems to still be alive. Ooguri makes a valiant effort to try to answer the question “If topological string theory is an answer, what is the question?” He does answer the question “If string theory is an answer, what is the question?”, but the answer is disappointing: “What is string theory?”

Jacques Distler is blogging from the conference. In his coverage of this morning he ignores the topological string theory stuff and describes Eva Silverstein’s talk. She seems to me to be getting into Bogdanov territory with an obscure mechanism that somehow is supposed to say something about the initial singularity of space-time. Jacques says he doesn’t really understand this, and I’m in agreement with him there.

And my logs are starting to show some connections from user37-*.wireless.utoronto.ca. Hi guys! Come on, there are at least nine of you reading this from the lecture hall, so at least one of you can tell us what is going on. String theorists seem to prefer Macs, so far the wireless connections are coming from 6 different Macs and 3 different Windows machines.

Thank you everyone for your valuable comments. Thanks to Peter for pointing out that I need to look at QFT and the standard model further and “anonymous” for taking time to find the links of the CDT papers.

Originally, I had an inclination to look at string theory as I was told that string theory is the only way to explain nature. When I asked what if its wrong, the string theorist I talked to explained that the contribution that it had made in mathematics is already so incredible that even if the whole thing turns out to be wrong its contribution would not go as a waste.(not a very satisfactory answer).I dont consider that I have reached the stage where I can declare to myself what is right and wrong. But I dont want to be a string theory fanatic (for that matter any theory) and hopefully be able to look at all the things with proper guidance.

Hi FineStructure,

I’m also trying to tackle this material on my own (even if it takes ten years). That is impressive you were able to do Polchinksi and Zwiebach. I took one look at Polchinksi and realized there were about six other subjects I had to learn first.

I wish you luck on your studies.

Mike

You write:”Jacques Distler … describes Eva Silverstein’s talk.

She seems to me to be getting into Bogdanov territory..”

I wonder…have the Bogdanovs ever dared to give a

talk about their ‘scientific work’ with experts as audience?

At a conference?

“All I want to find is the truth” said a youngster. Yes, we were all like that. Sooner or later you’ve got to develop some ability to think for yourself.

-drl

dan:

will you be blogging loop 05?friendly question, encouraging of you to ask!

October is too far away to say for sure.

Probably not, but hopefully someone will be.

thanks for the discussion “at”.

sounds very promising.

will you be blogging loop 05?

By way of another shameless self promotion let me just mention that two news correspondents of the String Coffee Table are currently liveblogging at least some of the Streetfest.

By way of shameless self promotion let me just mention that I intend to liveblog at least some of lattice 2005 (the Plenary sessions), starting July 24th.

dan:

do you think, given its good semiclassical limit, there will be an exodus from LQG and spin foams to CDT? (i.e smolin thiemann markopoulou?)I will tell you what I think. You may look at the same bunch of researchers and see quite a different picture. In my view, (non-string) Quantum Gravity is a single research community and divsions within that are fairly fluid. Loll has written LQG papers, both Smolin and Markopoulou have written CDT papers. The spin foam sum over histories approach has some resemblance to the CDT path integral.

the people who do (nonperturbative background independent) Quantum Gravity are allied by having similar concerns and familiarity with each others’ methods—you might think of the different methods represented at the Loops 05 conference as a menu or as a repertory, and anyone who wants to do nonperturbative quantum gravity can choose from that menu of tactics.

Probably this year Loll’s new results will attract a lot of attention and the others will see if they can get similar results (with causal sets technique or spin foam) or if they can adapt CDT to what they do, or they will move over and try CDT approach proper.

Loll is just beginning to do black holes with CDT, and there are others who seem further along with that. Loll is also just beginning to include controlled topological variation in the path integral (so that it sums over topologies instead of just over the geometries of a fixed topology). People who use other methodology will want to know about that.

Collectively the (non-string) Quantum Gravity community is in a period of rapid growth, each year more people and more papers. I presume that will continue. I cant predict much about the demographic shifts WITHIN that community because people change back and forth and may even work several lines.

hello “at”

i read the links on loll’s CDT, and i see a claim is made it has a good semiclassical limit (unlike LQG, spin foam, etc)

while i understand LQG is based on asketar’s new variables quantized version of GR, it’s not clear to me how CDT starts and how it quantizes GR, what sort of predictions it makes at high energies/planck scale etc it seems clear to me it is unrelated to LQG.

do you think, given its good semiclassical limit, there will be an exodus from LQG and spin foams to CDT? (i.e smolin thiemann markapolou?)

can you enlighten me?

dan:

I am curious as to whether anyone thinks the Loop 2005 conference will show progress and/or results,..Personally, I think it will show progress and results and can point you to papers that have appeared since the last conference (which was May 2004) which I consider significant.

But first notice that the Loops 05 website does not define the conference as confined to LQG but rather says:

“the annual international meeting on

non-perturbative/background independentquantum gravity takes place from 10-14 October 2005 …”http://loops05.aei.mpg.de/

And notice the topics listed on the homepage, where it says:

“The topics of this conference will include:

Background Independent Algebraic QFT

Causal Sets

Dynamical Triangulations

Loop Quantum Gravity

Non-perturbative Path Integrals

String Theory”

As it happens, both Laurent Freidel (a paper of whose Peter mentioned here earlier this year) and Renate Loll are invited speakers and members of the organizing committee. Loll is associated with research in CDT (causal dynamical triangulations) which is a nonperturbative path-integral approach to QG.

If you want a sampling of recent progress and results bearing on the Loops 05 conference, just go to arxiv and look up the papers of Loll and of Freidel which appeared since May 2004. Then you can form your own estimate of the significance of the work.

I am curious as to whether anyone thinks the Loop 2005 conference will show progress and/or results, esp in comparison to String 2005, both from what has happened before, and in comparison to one another.

QFT is in some sense a very large subject, being used in condensed matter physics as well as high energy physics, as well as mathematics. So it might be too broad a topic for a conference.

But there’s also an attitude among particle theorists that QFT is a completely understood subject, and that the only people who still think about it are those that are just not smart enough to do string theory, which is the real cutting edge stuff.

I can tell you what will be going on at Strings 2005 without even being there, Peter: same old, same old.

Why should it be otherwise? The expected, wonderful breakthroughs in string theory have been failing to materialize since the event began in 1997. When the time comes, perhaps comparing the content of Strings 2007 and Strings 1997 may demonstrate what actual useful ‘progress’ string theory has made in the preceding period.

I’ve wondered for some time why there never was a large annual conference on QFT (named, perhaps, ‘QFT’). Is it because QFT is considered a dormant, completely understood topic in theoretical HEP? Is a large portion of the theoretical HEP community implicitly promoting this erroneous opinion?

John Baez has written a useful web page entitled How to Learn Mathematics and Physics at http://math.ucr.edu/home/baez/books.html

A nice book ( based on Sidney Coleman’s Harvard lectures and Robert Brandenberger’s official homework solution sets ) is Quantum Field Theory for Mathematicians, Cambridge University Press, Cambridge, 1999, by Robin Ticciati. John Baez describes it as “… Quantum field theory – so even mathematicians can understand it …”. However, be aware that an Amazon review says that the book has misprints, so be warned and take care reading it ( of course, any book should be read carefully because of the possibility of misprints ).

An older book that I like is Quantum Mechanics and the Particles of Nature: an Outline for Mathematicians, Cambridge University Press, Cambridge, 1986, by Anthony Sudbery, but it is hard to find ( Amazon says that it is not available now ). As John Baez says, it is “… Not just for mathematicians! …”.

Tony Smith

http://www.valdostamuseum.org/hamsmith/

To anyone who shows up at Strings2005 with a laptop: yes, please post comments. Put “connectivity” to a good use.

what should I do before I go too farMy personal experience, I went first far into another branch, non commutative geometry, and now I have found myself looking at traditional QFT, the standard model, model building and all that. (Somewhere in the middle I read the Green-Swartz-Witten, but it did not convince me).

QFT books do not always provide a decent instint in model building, nor on HEP scattering, but they are always a better startpoint that strings or other mathematically minded setup. After managing them, you can confidently venture into more theoretical enterprises. I hope to retake NCG, but by now I have understood how different is the third generation from the two first ones, or how naive is to blindly hope a single higgs doublet. Nor to speak of surprising mass regularities, or the lack of some a priori expected energy scales (eg why the muon and the tau live at well known hadronic energy scales, the muon so near of the pion?), or the Nambu “alpha” principle to hierarchise masses… a lot of things you only learn by playing with the data, and man, I just wished to be more fluent on standard QFT when juggling these balls.

If you’re an undergraduate, after you have a solid background in quantum mechanics, EM, classical mechanics, general relativity and thermodynamics, you should start trying to seriously study quantum field theory (using books like Peskin and Schroeder, Zee, Weinberg, Ramond, others), and the details of the standard model. Really understanding QFT and the standard model is more than enough for even the most ambitious of undergraduates. You should also learn some modern geometry and topology.

It’s kind of absurd to be studying string theory if you don’t already have a solid understanding of quantum field theory, and that’s a very non-trivial project which can take a few years.

Fine, I said I’d get some links, on the off chance you wanted to check out some CDT papers

here’s the entire CDT output for the past 12 months, it is only 8 papers

http://arxiv.org/find/grp_physics/1/OR+OR+abs:+AND+triangulations+AND+Lorentzian+dynamical+abs:+AND+triangulations+AND+causal+dynamical+ti:+AND+gravity+AND+Lorentzian+quantum/0/1/0/past/0/1

and you can actually narrow it down to those co-authored by R. Loll

http://arxiv.org/find/gr-qc/1/au:+Loll_R/0/1/0/all/0/1

and of those, the most recent summary of results is

http://arxiv.org/abs/hep-th/0505154

Fine asks

However well if string theory is not the answer what should I do before I go too far and become not willing to see anything else.no authoritative answer, but my personal response would be you should check out the picture of quantum spacetime coming out of CDT (causal dynamical triangulations, one of the quantum gravity alternatives to string)

there are only a small number of papers to read, most of which appeared in the past year and a half.

I will get some links. It is a path integral “sum over spacetime geometries” approach where they have both analytical and computer spacetime simulation results.

There is evidence that their spacetime agrees with classical GR in the large, and with prevalent semiclassical “quantum cosmology” near the cosmological singularity. And also that their spacetime is highly unclassical at small scale. (may be fractal-like or topologically complicated at very small scales — probably not describable as a differentiable manifold)

So at least it is different. and immediately accessible.

the “question”, I suggest, is how should quantum spacetime be represented mathematically? because only once there is a satisfactory spacetime foundation can particles/fields be reconstructed on that basis.

If String Theory’s the Answer, What’s the Question? I am an undergraduate and I have already put in lot of energy and time trying to understand string theory from Polchinki book and Zwiebach book to a lesser extent. Also, I check most conferences in String Theory. Recently,I have been following Peter’s blog (for a month now)I have been skeptic of string theory for a while. All I want is to find the truth. I guess ultimately I have to find the answer to this question for myself. However

well if string theory is not the answer what should I do before I go too far and become not willing to see anything else.

About the Landscape, I was thinking… if instead the anthropic principle, we use the humbler “Standard Model at Low Energy Limit” principle, how large is the remaining landscape? Still infinite dimensional? Finite? Null?

If String Theory’s the Answer, What’s the Question?Suggestion:

“How does a bright, sceptical young scientist turn into a raving, pseudo-religious moron?”