dynamical models

Widrow, Foreman-Mackey, and I spent a bit of the morning discussing the best approaches to dynamical modeling in the short term. I am in favor of non-parametric modeling of the distribution function, and then marginalization. This is hard, because non-parametric models have enormous numbers of parameters. But I don't see any other principled method, and the nuisance parameters definitely matter. However, Widrow suggested that we could start with parameterized models, based on things that are known about potential-density pairs. This is a good idea, and we can use it to test assumptions; in particular we can see if, in toy systems, you get wrong answers about the potential if you use overly simplistic distribution function models.