Ah, a day where research dominated; the first in a long while. I spent the morning up at Columbia for NYCastroML, where we discussed regression and cross validation. I am a huge supporter of cross validation. We spent some time arguing about the difference between regression, fitting, and "learning". Most importantly, we came up with some good rules of thumb for doing stats in astronomy, and I hope very much someone wrote them down!
After that, Foreman-Mackey and I came downtown for a meeting with Greengard, O'Neil, Ambikasaran, Fadely (all NYU), and Epstein (Penn) about the possibility that we should be propagating the Good News of Ambikasaran et al out to various scientific domains, like machine learning, astrophysics, and neural science. We agreed to search out places where people want to use Gaussian Processes but are stuck on the computational complexity.
Late in the day, Sven Kreiss (NYU) gave a great PhD defense talk on his work on the Higgs at ATLAS. He showed how it was discovered and how its mass was determined. In both of these important results ("Breakthrough of the Year" at Science), he had a leading role. A great PhD and very well deserved, Dr Kreiss.