Citations: Dyonic Black Holes, Landau's Hydrodynamics

A few months ago I posted a proceedings from the GHP06 meeting in Nashville, called "Hotter, Denser, Faster, Smaller...and Nearly-Perfect: What's the matter at RHIC?" In general, people don't cite proceedings much, since they often just summarize results from other papers, maybe combining a few things here and there that hadn't been done before, or making some useful (if not exactly rigorous) commentary. Now why the authors of "Hall conductivity from dyonic black holes" (Hartnoll and Kovtun) chose my proceedings to cite in their paper -- beyond the fact that I cite and show a figure from Kovtun's seminal work with Starinets and Son -- I don't know, but I think it's really neat to be introduced to a new physics topic via my own citation-searching vanity. RHIC physics is starting to make its presence known to more and more communities, since it is now finding itself friends with many different kinds of strongly-coupled systems -- and it's really bracing to watch it happening in real time (vs. summarized in textbooks years after the fun is over).

And speaking of citations, I also just noticed a recent paper "Unified description of Bjorken and Landau 1+1 hydrodynamics" citing my old proceedings on "Landau Hydrodynamics and RHIC Phenomena". I'm still trying to figure out exactly when the switch in my brain flipped in this direction, but I've been arguing (only semi-successfully) for about four years now that people should be taking Landau's hydrodynamical model (full stopping of the nuclear matter in the overlap volume) seriously, following the clear lead of Peter Carruthers in the 1970's. It's been known for a while that some RHIC data clearly supports it, and I've argued that a wide range of phenomena are also consistent with it, but very few people have done theoretical work to see how it behaves in the geometries we might expect from nuclear collisions.

Thus, this new paper is encouraging to see, since it at least revisits and starts to clarify how the Landau solution "works". It's also neat to see more and more people exploring the connections between hydrodynamic behavior and dual gravity theories. One of the authors of "Unified" proposed boost-invariant (Bjorken) flow as being dual to a black hole moving in the "5th dimension" of the AdS theory, which begs the interesting question of what the equivalent analogy is for Landau's fully 3D flow (which is a much more interesting scenario than boost-invariance since it provides causal connections between most of the final state by rapid thermalization in the initial state -- a lot like the inflationary model of the universe!). I hope these guys figure this out, and soon.