Saturday, June 24, 2006

Wrapped Strings

Three weeks of string school and strings conference has now come to an end and I'm feeling a little weathered by it all. I'm attempting not to lose the momentum I've built up by actually going through the notes from the school, a task which I always promise to do but something else always seems to come up. In less than a week a friend from Japan will come over and we have some project ideas that we will be working on for a couple of weeks so it's now or never in terms of consolidation.

Anyway, there are too many other things to do right now to write reviews for the other talks but the least I can do is to summarise the summary presented by Robert Dijkgraaf at the end of Strings '06.

He started by illustrating the various football tactics of the countries in the world cup (if you haven't seen this then e-mail me and I'll send it to you), England's one man strategy, Germany's direct efficiency etc. This also included China which has nobody on the pitch at all (though this was altered by completely filling the pitch with white dots). He then explained that a similar picture could be drawn for string theory where the players on the pitch are the many areas of the subject which have been discussed over the last week, culminating with a possible goal from LHC. Added to this was the possibility of success for loop quantum gravity, though this tactic ended with an own goal, and rapturous applause.

Robert spoke about the landscape of ideas which is filling the stringy world at the moment and in particular the great intellectual diversity which is allowing technical progress in many long standing problems.

Again, the hope was echoed that LHC, astroparticle physics and the next generation of microwave observers may give us real signs of string theory in the coming years (see Sarah Shandera's talk for details).

The first subject which he said had been at the forefront of many talks in the meeting were the new developments in dynamical supersymmetry breaking and the control we have over this now using things like the Seiberg duality relations. The main point seems to be that we no longer have to come up with some convoluted mechanism for this phenomenon but rather dynamical SUSY breaking is generic in both QFT and string theory.

Next was the work on non-SUSY black holes and the attractor mechanism for these solutions. The question now seems to be what is the microscopic description of such objects.

Also on the topic of black holes was the subject of quantum black hole entropy and the important steps we have taken towards understanding N=2 black holes. Strominger's intuitive derivation of the OSV conjecture in terms of a gas of branes and antibranes was cited.

Again, black holes, but this time in terms of a probe of quantum gravity physics in terms of the recent work on bubbles of meta-stable vacua and bubbles of nothing in Kaluza-Klein black holes.

Another important topic was that of the real possibility of solving perturbative N=4 SYM in the large N-limit using the spin-chain formalism. Though I haven't written about it yet, there were talks about the all loop Bethe ansatz and integrable scattering of magnons and strings in AdS_5xS^5. In terms of quantum gauge theories, the emergent geometry from matrix models, thermal instantons and open strings was discussed as important new insights.

Closer to home, the Standard model was spoken about in terms of the model building on del Pezzo surfaces, D-brane realisation of the MSSM and coisotropic branes on toric orientifolds (I'm simply quoting the last statement without a true understanding of it). The fact that we should certainly have data from the LHC within three years is exciting for all the obvious reasons.

Next was the topic of landscape gardening both from inside and out. Vafa's work was cited as 'The Geometric Swamplands Program' and this, along with more studies on the distribution of vacua (plus Douglas et al's recent work showing the finiteness of the number of vacuum solutions) go some way towards understanding what we can and can't have in a theory of quantum gravity.

Seemingly the most likely candidate for really seeing stringy effects are in the realms of cosmology and in particular the CMB where stringy signatures in non-gaussianity and tensor-scalar ratios will perhaps be detectable when Planck comes online. Also Jonathan Feng's work on superWIMPS was mentioned as a possible detectable form of dark matter at the LHC.

Next was the work on topological string theory and how there is currently such a huge richness of mathematics coming from the subject. This work includes the result of a closed formula for an all genus amplitude on a compact Calabi Yau being imminent.

More on the mathematical side of things were the topics of the geometric Langlands program, more generalised stringy geometries and Sergei Gukov's work on categorification (again I'm just quoting there, I don't claim to have a good handle on that talk even though sergei is an excellent speaker).

On more isolated points were the fact the Martin Schnabl has proved two of Sen's three conjectures using open string field theory, the work of Nekrasov on topological quantum field theory and the fact that we are now going beyond the study of half BPS states and Jerome Gauntlett's work on a new, infinite family of supergravity backgrounds.

The point was made that with both the Poincare conjecture and Fermat's last theorem being solved in the last decade, this really seems to be a golden age of mathematics. Can it also become a golden age of physics?

Reading through all of that again I'm not surprised that my brain is feeling a little bruised. It seems that there have been many exciting steps towards understanding a great number of areas of string theory, quantum gauge theories, black hole physics and mathematics and we are very close to understanding some deep long-standing problems. The prospect of particle and cosmological searches for stringy signatures is an extremely exciting one.

Finally Robert spoke about some of the problems of the conferenece. These were all things which were lacking, including front page headlines in the New York Times, no voting, not enough jokes in the afternoon sessions and little in the way of 'metaphysical multiverse babbling'. One particularly important point was that being behind the great firewall, people could read Peter Woit's blog but not Lubos Motl's!
Finally it was noted that David Gross gave a talk which didn't go far overtime and Yau gave a talk which was extremely comprehensible.

Robert was not given an easy task to sum up everything from the last week (which itself was a summary of the last year) into just half an hour but the above points which he made seemed to set the tone of the last six days pretty well.

Now everyone is heading back to their various corners of the world, many I presume with new projects, insights and collaborators.

This has been my first strings conference and I have to admit to feeling quite far out of my depth most of the time though by chatting with people about the talks I've had many long-standing questions answered for me. I presume that each time I go to a conference and talk more with physicists in diverse areas that my understanding will grow. This has also given me some more impetus to learn some of the areas which I've neglected while concentrating on my own particular pet topics. It's been great as well to see friends from conferences I've attended over the last few years and I look forward to catching up with them again soon.

Though hopefully I will add some final reviews over the coming days, the physics content of this blog may lighten up a bit for a while. Right now I have to head outside where the Beijing weather is throwing another wobbly as detritus is zipping past my window at dizzying speeds and dust devils are swallowing the workmen building the skyscrapers surrounding my apartment. Baksun.


Anonymous said...

Hi Jonathan,

Lubos Motl's blog certainly can be
accessed in China via the mirror

Unknown said...

Hi, yes I'm aware of the mirror. Unfortunately many people don't seem to know about this (understandably as they don't usually need it). Also, the mirror site is out of date by a couple of months, or at least it was yesterday.

All the best,