Strings 2009: public lectures

The annual stringy conference in Rome has ended. A large part was dedicated to applications of the AdS/CFT correspondence in nuclear physics, condensed matter physics, and related realms: these methods have grown into a mature, well-established industrial sector which is both a good thing (because it works very well) and a bad thing (because it works too well and the main qualitative dreams have probably already been uncovered and the activity has become a routine).



Several talks were focusing on the booming field of F-theory bottom-up phenomenology - which has already arrived near the "top" because the constructions are already trying to construct the full compact manifolds - i.e. global models - not just the local map of the vicinity of the relevant singularities. I think it's very helpful that those several groups that work on this highly promising possible incorporation of the real world within string theory were forced to meet because I found the degree of interactions between these big shots less frequent than desirable. We'll see where their work goes.

By the way, Marsano, Saulina, and Schafer-Nameki released their new paper yesterday. It is constructing the full local F-theory compactifications that obey all the geometric constraints that were pointed out to naturally cure many problems of supersymmetric grand unified theories and predict many of their additional features such as various mass hierarchies.

It is almost possible to naturally explain all these patterns.




However, they showed that the F-theory framework is insanely predictive, indeed. In fact, it is so predictive that if they combine all the geometric expectations about the F-theory manifold that have been proposed during the last year, they can show that the realistic neutrino masses cannot emerge in the way described by other recent F-theory papers (because of missing and/or unwanted U(1) gauge groups). In other words, the total set of constraints that have been independently imposed in many papers is too strong and can't contain a realistic model that satisfies all the constraints at the same moment. Not to be excluded, some of the constraints have to be weakened: it is a highly constrained setup.

Let's return to the conference. Add Nima's talk about holography in the flat space (and twistor-related convergent properties of the S-matrix continued to the 2+2-dimensional signature), talks about finiteness of N=8 SUGRA, integrability of N=4 Yang-Mills, AdS4/CFT3 talks building upon the recent membrane minirevolution, attractors and advanced black hole entropy topics, links to the LHC, and Petr Hořava's lecture about the Hořava-Lifshitz gravity which was arguably concerned with the most unusual and least believable - you could say "most provoking" - paradigm on this conference, almost playing the role of Rovelli's talk in 2008 ("almost" because Petr works with a system that at least contains a spacetime).



Edwin Cartlidge (click) of the Physics World described some public lectures today - except for the lecture by Gabriele Veneziano about the beginning of time which was in Italian.

Nicola Cabibbo, the owner of the well-known angle (who was only denied the latest Nobel prize because, well, Nambu deserved it somewhat more than he did), gave a very non-technical, popular or even populist talk (as Moscadelburro observed) and introduced Edward Witten and Brian Greene.

Witten, perhaps influenced by his stay at CERN, focused on the LHC expectations, including supersymmetry. Moscadelburro said Hello to Witten! ;-) Brian Greene apparently gave a somewhat standard but formally optimized, state-of-the-art, multimedia, movie-quality introduction to string theory, adding that the existence of googol^5 vacua suddenly looks as a likely way to explain the smallness of the cosmological constant.