The day started with a short conversation with Anna Ho (MPIA), Foreman-Mackey, Ness, and Rix about changing the polynomial model inside The Cannon into a Gaussian Process. This move (which Ho and Foreman-Mackey are attempting this week) brings a large number of advantages: It makes model complexity a continuous problem rather than a discrete problem, and it permits us to continuously tune model complexity at every wavelength. We are violating all the usual rules though, because although at training time we are doing standard Gaussian Process regression, at test time we are doing the inverse of Gaussian Process regression! That's a bit crazy.
In late morning, Susan Kassin (STScI) told us about simple measures of galaxy dynamics and the formation and evolution of the Tully–Fisher relation. She busted some galaxy-evolution myths. What she has been doing so successfully at high redshifts (out to one), the SDSS-IV MaNGA project will do at low redshifts (and much more).
I talked to Foreman-Mackey over lunch (and over 4000 miles) about single transits. He has developed (in partnership with Schölkopf) a machine-learning methodology for finding them and understanding both completeness and false-positive rates. We discussed the issues and scope for a first paper, which would create a complete catalog for the main-mission Kepler data.
I also gave comments on current drafts from Malz and Vakili, and had a long conversation with Wandelt (IAP) regarding probabilistic approaches to cosmology. I pitched my project to evaluate a non-approximate likelihood function in real space for CMB maps and he agreed that if we could show that a full likelihood function evaluation is computationally tractable, it might influence the next generation of analyses.