The prettiest hep-th preprint today is the last one and it was written by Clay Cordova at Harvard,
A crash course on F-theory singularities and Fano threefolds is included. I guess that it may be useful for many readers to learn this material from Cordova. You know, if a high school student from 2003 knows such things, maybe we should follow, shouldn't we (despite the fact that all Fano threefolds are ultimately ruled out in the paper)? ;-)
But what is truly remarkable is the design of his paper. For example, this is the figure 1 with the general sketch of the branes within the F-theory compactification manifold and their intersections.
Click to zoom in a little bit. It's kind of logical that because F-theory is, in some sense, a 12-dimensional theory, the pictures should try to be multi-dimensional, too. ;-) After having read the paper, this guy clearly know what he's doing. He should only learn how to spell Planck correctly. :-)
However, I still feel that his requirement of the decoupling of gravity is too strict. Seven-branes carry the deficit angle of pi/12 and he wants to locally cancel it, by adding orientifold plans on top of the branes. Well, I would think that he should only try to decouple the propagating modes of gravity rather than the fixed contributions to the curvatures and deficit angles.