Strings 2013

Guest blog by Daniel Grumiller of ITP Vienna, a participant

Lubos asked me if I would write a short summary of Strings 2013, and since I appreciate the cohomology of his blog [all blog entries, modding out the non-physical state(ment)s] I decided to oblige.

If you are interested in the actual content of the talks I suggest you listen to them (or view the slides) here.




If you want an excellent and witty summary please watch Jeff Harvey's summary talk or view his slides. I cannot do a better job than Jeff, though I will add a few, mostly irrelevant, personal comments at the bottom of this text.

The outlook by the "higher authority" can be found here. The final conclusion by David Gross is that string theory is alive and kicking, with which I agree.




Here are a couple of miscellaneous comments, which I just add to convey an epsilon of the excitement that accompanied this conference, despite of the absence of "revolutions".

• Strings 2013 was extremely well-organized. While the same remark applies to some previous Strings like in Munich last year, this time everything went so smoothly that you hardly noticed the stress that inevitably comes with the organization of such an event. Much like good electrical wiring in a house, you notice that it is done perfectly through not noticing it at all, except that all the lights work.
• Seoul is an excellent venue. It is my first time here, and I enjoy very much the city, the culture, the excellent subway, the food, the hospitality and the alphabet.
• The talks were brilliant. Let me not rank them, except that from a purely aesthetic perspective Greg Moore's talk certainly won the first prize. Just look at p.2 of his talk. From a technical perspective, I was impressed by all the talks of the "younger generation" (see next item).
• Jeff Harvey provided a \(\ZZ_2\) classification of the audience into PhD before/after 1999 and gave two separate sets of three questions. If you have not done the quiz on p.9 of his slides you could do it now. Belonging to the young generation, I was tempted to give the answer "four" to his first question, but he was only counting down from three (ok, actually my answer to part of his tricritical question differs surely from what Jeff would have counted as the correct answer; I would have said that \(c=7/10\) is special since, together with \(c=1/2\), the corresponding CFT is dual to Einstein gravity in 3 dimensions)
• Given that I work on related issues it was great for me to see again the presence of higher spin gravity (Igor Klebanov's and Matthias Gaberdiel's talks, as well as David Gross' comment on his third big question). But I also enjoyed the variety of excellent review talks and selected technical talks. Inevitably, in some of the talks I felt a bit like in Jeff Harvey's (or Gary Larson's) cartoon on p.7 of his talk.
• The gong show was again interesting. If you do not know this format: every speaker has at most 5 minutes, after which the screen goes dark and the micro is switched off. There were 13 speakers. If this sounds stressful for speakers, organizers, audience and the chairman you get the right idea. It is still a good item at such a type of conference and impressive how much (useful) info some people can convey in this short time. The last gong-speaker, Michael Gary, gave an excellent summary of our \(W_N^{(2)}\) gravity paper.
• The banquet was phantastic, both from a culinary and a performance view point. I also enjoyed Neil Lambert's humor in his dinner speech, though I am not sure all his remarks were appreciated. He mentioned that he did not follow Jeff Harvey's 1998 Macarena/Maldacena performance with a "Gaiotto style" performance since Davide was absent, a remark which earned applause of relief. To compensate, the organizers displayed this video after the last talk today, while people were leaving the auditorium (I guess the non-younger generation left more quickly at that point).
• Strings 2014 will be in Princeton.

In conclusion, Strings 2013 was an excellent conference in every respect, in particular from a scientific perspective.

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The text below by LM was posted on 6/27.

Seoul, Korea is the place where the music for Newton's Pendulum Gangnam Style was born.



Xmphysics released the video above just 3 weeks ago. The most successful rendition of this song-plus-dance has attracted over 1.6 billion views on YouTube. Seoul is also the place where the string theory annual conference takes place.

Strings 2013: talks, titles, PDF, videos

The videos from the talk are being posted via YouTube: you should click at the blue video icon and then the Quicktime-like icon on the next page. Incidentally, I like the 1-second jingle at the beginning of the YouTube videos and I think it's sensible for conferences to post their videos via YouTube instead of various do-it-yourself video frameworks.

Those of us who are following what's going on aren't surprised by most of the topics that the speakers – famous and well-known enough string theorists – have been thinking about recently.

One of the 30-minute talks I am going to watch – I am watching it now, in fact – is Shamit Kachru's talk about the Mathieu Moonshine which I already mentioned in when it was discovered. The monstrous moonshine has been discussed on this blog many times; in string theory, the Monster group has been linked to a Leech-lattice-based compactification of string theory as well as the pure AdS3 gravity.

But the Mathieu group is one of the smaller sporadic groups among those 26 or 27 ones and the moonshine links it to some calculable properties of K3 compactifications of string theory. Shamit's talk is nice but he says some wrong things, too. For example, moonshine isn't called moonshine just because it is "enigmatic" but because Andrew Ogg promised a bottle of Jack Daniel's whiskey (moonshine) in his paper to the person who explains a moonshine-based relationship.

Otherwise, John Schwarz has already given an introduction you may watch. Nima Arkani-Hamed about their new way to calculate the gauge theory amplitudes. Shiraz Minwalla and Dan Jafferis chose topics related to Chern-Simons theory. Rob Myers, Juan Maldacena, and Tadashi Takayanagi talk about entanglement's links to holography and spacetime topology while Joe Polchinski tries to update the so far seemingly invalid AMPS discussion of the firewalls in particular and the black hole interior in general. He clearly tries to react to Maldacena-Susskind and I will study his talk in more detail later.

You can read all the titles and topics yourself, many of them are interesting.

I've watched Kachru's, Maldacena's, and Polchinski's talk. There were lots of interesting things in them but Joe's talk is just plain wrong. He believes to have a newer version of the AMPS argument – a direct proof that a generic black hole microstate must have every internal field-theoretical mode in an excited state, with the average occupation number well above zero (around 10:00 in the talk). This is, of course, bullshit. Even if you consider a relatively young black hole, much younger than the Page time, it's easy to see that the more empty the black hole is, the higher entropy it has. As it is initially losing some energy by the quasinormal/ringing modes, its entropy is still increasing. Once these ringing modes are emitted, the entropy nearly stabilizes – it gets maximized – and of course that the corresponding value of the internal field theory field modes' occupation numbers converges to zero in this regime. I am talking about field modes expressed in a freely falling frame. Of course that some accelerated observers will see Unruh's radiation whose modes' average occupation number is nonzero but this is not new and it doesn't contradict anything about complementarity. Polchinski concludes that CFT in AdS/CFT is an incomplete theory of the bulk. Holy cow. If AdS/CFT says something about the quantum gravity in the bulk, it's true and it's the whole story.

BTW Michael Gary (thanks, Daniel!) cleverly asked Joe what prevented the firewalls from destroying any place because it's the Rindler horizon. Joe answered that the states of the Rindler horizon that don't have the firewall are non-generic – generic states have it, too. That may be a cute way out but we may still consider the numerous states that don't have the Rindler horizon. Their entropy may still be high, within this set, there's no firewall, and this set may still be analogous to all the black hole microstates in the black hole case. Andy Strominger said that there should also be other ways to see the firewalls if they existed. Joe interrupted Andy before Andy asked the question but the question was finally asked, anyway. Joe tried to answer the question by mixing firewalls with fuzzballs. Just to be sure, Sumir Mathur of fuzzballs considers Joe's firewalls wrong. Andy asked why the firewalls were a quantum gravity issue – as it is claim to invalidate arbitrarily large black holes in GR. Joe answered that he believed the nonlocality in QG to be arbitrarily brutal. This is clearly a doomed attitude because classical GR is one of the defining features of the general concept of QG and if we can't isolate any subset of regimes in which classical GR applies, then the notion of QG is clearly insufficiently constrained to be well-defined. Daniel Harlow made similar comments etc.

I will probably watch some talk about a solid discipline to improve my tastes, e.g. Xi Yin's talk...