KIPAC Seminar: Towards a Standard Model of the Milky Way Disk: Kinetic Theory, ISM Fluctuations, and the Radial Velocity Wave

The cosmology and particle physics communities have each developed extremely successful 'Standard Models', capable of fitting huge amounts of data within a single, well-defined mathematical framework. Likewise, observations of the Milky Way are now so advanced that we may begin to speculate about constructing a Standard Model of our Galactic disk's evolution. Unfortunately, our theoretical tools are not yet good enough for this task. In this talk I will discuss the two broad regimes in which theory needs to improve if we are to make this ambition a reality. First, we must understand the slow, secular evolution of the disk's (quasi-) equilibrium distribution function over billions of years. I will show recent results suggesting that classic ideas about this process -- especially the role played by ISM gas -- might need to be revised. Second, we must understand the short-timescale fluctuations in the disk chemodynamics that have been so beautifully unveilied by Gaia. I will share a promising new semi-analytic approach to investigating these fluctuations, focusing on the 'radial velocity wave' as an example. Finally, I will speculate on how we might bring these ideas together to write down a Standard Model for our disk --- and perhaps even an effective field theory of galactic disk dynamics beyond the Milky Way.