I spent time today with Christina Eilers (MPIA), discussing how to constrain the Milky Way disk potential (force law) using the kinematics of stars selected in a strange way (yes, APOGEE selection). She and others have shown in small experiments that the radial angle—the conjugate angle to the radial action—is very informative! The distribution of radial angles should be (close to) uniform if you can observe a large patch of the disk, and she finds that the distribution you observe is a very strong function of potential (force law) parameters. That means that the angle distribution should be very informative! (Hey: Information theory!)
This is an example of orbital roulette. This is a dynamical inference method which was pioneered in its frequentist form by Beloborodov and Levin and turned into a Bayesian form (that looks totally unlike the frequentist form) by Bovy, Murray, and me. I think we should do both forms! But we spent time today talking through the Bayesian form.
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