Strings 2006 day 4, parts b and c

Since visitors to this blog have increased 15-fold over the last week I feel particularly bad about not keeping up with the overview of the lectures. I've been taking the fantastic opportunity of this week to talk and build up my collaborations with other physicists. This is something I get to do very little when in the department in Beijing though I'm hoping that that will change soon. The work outside lectures has so far been taking up an enjoyable large part of my time. Together with a PhD student from Munich I'm investigating a couple of new projects which could be really exciting if they don't turn into dead ends. It's also a great chance for me to meet some more of the Chinese string theorists.

Together with the fact that after three weeks of lectures I'm feeling pretty tired, especially in the sizzling temperatures, I haven't been posting as I'd hoped. I have however hopefully roped a couple of other people into reviewing some of the talks which I missed either physically or mentally and hopefully I'll be able to post those over the next couple of days.

For now, after another gruelling day and a conference banquet with perhaps 10 speakers all singing their praises of the organisation of the committee I have enough energy to talk about a couple of the talks in brief. The speakers during the dinner were in large part talking about the rise of physics in Asia and though a large part of this was related to India, Japan, China and Korea, it was noted that those who are sharply on the rise ought to be helping all those countries who are currently not getting a look-in on the world science-scene. Wise words indeed. It was also posited that by 2010 Strings should perhaps return to an Asian country and Korea was briefly whispered. The next three years the conference will be in Madrid, Geneva and Rome, all of which are fine venues but certainly 2010 away from Europe seems wise.

Today Andy Strominger gave an interesting talk about the proof of the OSV conjecture which links the partition functions of black hole states in IIA string theory with the partition function for a the square modulus of the partition function for a topological string theory. This was a seven step proof which I shan't be able to reproduce here but is shown in full in this paper. Essentially this comes from studying the sum over near horizon bound states of D4-D2-D0 branes and then lifting to M-theory. The partition function has two contributions, one from wrapped M2 branes and one from wrapped anti M2-branes and it's these two contributions which give Z_top and Z(bar)_top to give the surprising relationship between the partition functions. Apparently in progress is a direct derivation of the OSV conjecture using GS formalism on the worldsheet.

Yesterday morning was a good talk from Juan Maldacena on Giant Magnons. In very brief summary this is related to the spinning string - spin chain link of Tseytlin et al and what has been found is a particular solitonic mode on the spin chain called the giant magnon. In fact in looking around for more information I came across a nice review of the subject by Lubos Motl here.
I don't think I could do any better than simply link to his site though if I can rope someone into writing more then I shall do so.

Shiraz Minwalla gave a talk today in his usual frenetic style about calculating the full SUSY partition function for N=4 SYM compactified on a 3-sphere. It appears that they have calculated this for everything up to the 1/8th BPS states and the 1/16th states are currently in progress. The calculation of these states is related to the giant graviton modes. Looks like some great work but unfortunately though his speed of delivery is exciting, it's just too fast for me to keep up.

Other talks to review are an impressive stand-in for Henry Tye by his student Sarah Shandera, Martin Schnabl on the analytic results in string field theory, Hawking on why string theory is completely unnecessary for cosmology (some, in particular Raphael Bousso, may disagree with some of the points of this talk ;-). Also a couple of interesting talks about emergent geometry to review.

OK, lots more talks to write up but another early start tomorrow with many interesting seminars so I'll leave it at that brief summary for now.