This morning we had the lab
session; I had the students write from scratch a cross-validation code for model comparison. The model and optimizer we were using were not so good, so some of the code didn't work very well, but I learned a lot. I hope the students learned something. We tried to figure out if HD104067 has one companion or two. It was a pleasure to have Robert Lupton (Princeton) in the room, as he was tough on my code and also interjected some very useful stuff. Just before the lab session, Aigrain talked about Gaussian processes, showing some absolutely amazing examples from Rasmussen's book.
In the afternoon, there were many excellent talks; too many to mention individually. One highlight was Kitaura (Garching), who is very close to achieving the goal I have of performing properly marginalized measures of cosmological density fields. He might be able to take us away from point estimates of the correlation function! Ascasibar (Madrid) showed a very nice visualization of the positions of galaxies (relative to one another) in spectrum space. He is using some simple tools and finding some nice structure; much of the discussion after his talk was about the possibility of finding sharper tools and maybe even more dramatic results. Matthew Graham (Caltech) gave me a shout-out about not trusting meta-data and only working at the raw pixels (when I can). Christlieb (Heidelberg) showed some astounding spectra from large surveys and discussed how hard it might be to find and understand oddities in the next generation of million-spectra surveys. He included APOGEE in his list of important new surveys, to my pleasure.
There has been a bit of Bayes vs non-Bayes arguing at the meeting, and I have tried not to enter into it. I am a Bayesian, but I am also a pragmatist (and I am also willing to concede that its subjectivity is an issue for many, and not unreasonably). In the long run, we should be optimizing our long-term future discounted free cash flow.
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