Each summer for nearly a quarter-century there has been a big yearly conference bringing together the string theory community. I’ve often written about these conferences on the blog, see here. This year’s version will be held next week in Vienna, for more information see here.
Taking a look at the program, one thing that stands out is that the string theory community has almost completely stopped doing string theory. Looking at the program, only two out of 44 talks seem to be significantly about string theory. One of three parallel discussion sessions is entitled “Strings and the Real World” and will be chaired by Cumrun Vafa. I’m guessing this will mostly be about the swampland, not string theory.
A tradition at these conferences is one or more public talks designed to publicize string theory. This year’s versions will be given by Netta Engelhardt and Andy Strominger. They have nothing to do with string theory, but they do make very clear what the string theory community has found to replace string theory: black holes. Engelhardt’s title is “The Black Hole Information Paradox: A resolution on the horizon?” and Strominger’s is “Black Holes: the Most Paradoxical Objects in the Universe”.
Looking at the talk titles, the most common words in the titles are “holography” and “black holes”, with the center of gravity of the subject now for a couple decades the effort to use holography to say something about black holes. Maldacena’s title is “What happens when you look at supersymmetric black holes for a long time?” which seems also an interesting question about the field itself.
Update: Paolo Bertozzini points out to me that the LQG community has scheduled its big yearly conference LOOPS2022 at exactly the same time as the string theory community one (this week). It’s quite interesting to compare and contrast the two sets of talks. There are some very broad similarities between what both communities are doing, with overlaps in interest around black holes, entanglement, holography (in the form of large symmetry groups at infinity). Another commonality is that both communities are focused on the gravitational field, with nothing to say about particle physics and matter in general. This has been true of LQG since the beginning. In the case of string theory the big selling point originally was that it gave a theory of matter, but the string community has for a long time given up on that. There is a difference in how the communities think about “what are the fundamental degrees of freedom for gravity?” On the string theory side they’ve given up on that, the answer now is that gauge-gravity duality and emergence are supposed to allow you not to care about fundamental degrees of freedom. On the LQG side, people are still hard at work on specific sorts of degrees of freedom and how to quantize them.