Northwestern

I had a great trip to Northwestern University today, where I visited the CIERA, which is an interdisciplinary center for engineering and applied math and computer science and astrophysics. I talked about hierarchical inference.

Many of my conversations were about parameter estimation and inference using MCMC, where the group, including Will Farr, Ben Farr (no relation), and Vicki Kalogera have been doing pretty radical MCMC things for LIGO and other projects. In particular, Ben Farr told me about generalizations of parallel tempering that are extremely relevant to things Goodman and our NYU MCMC group have been discussing; it might make us infinitely powerful (or an approximation to that). Will Farr shares my love of "detecting the undetectable": He showed that you can infer the properties of stellar clusters even when no member is identified at high probability, which is one of the punchlines of the work I did (so very long ago) with Koposov and Rix. The Farrs also failed to dissuade me from (encouraged me towards, actually) signing an MOU with LIGO and doing some noise modeling.

Nick Cowan told me about mapping exoplanets using photometric variations and—in transiting cases—details of the lightcurve at ingress and egress. This is very related to the computer vision projects we were talking about this summer. I gave him this insane paper. He explained to me something I hadn't thought of at all before: The obliquity (angle between the rotation axis and the orbital plane) and the observational inclination (angle of the orbital plane to the line of sight) both enter in what you can see, so in principle you can measure obliquities (poorly) just by looking at phase curves in reflected light!

Late in the day, Meagan Morscher and Laura Trouille told me about their work on computational thinking, which is something I ought to muse about on the teaching blog.