In the morning Keith Hawkins (Cambridge) showed up for my group meeting. He made the strong argument that if we could measure stellar ages, we could see structure in the Milky Way that won't be revealed by (blunt) chemical tracers alone. I agree, and he came to the right place!
In the afternoon at the SCDA, Charlie Epstein (Penn) gave Magland and me some very good arguments or intuitions about the chaotic map we have been playing with in the phase-retrieval problem. He argued that the projection operators can be designed to greatly increase the effective overlap of sets for which the map is looking. Recall that the goal is to find the overlap of two sets. In the conversation, he effectively generalized the concept of “reflection” (which might be, for example, across a line) to the equivalent for any kind of set (that is, for things other than lines and points). Awesome!