Swing Amplification and the Gaia Phase Spirals

Abstract: The stellar disc in the solar neighbourhood appears to be in a state of disequilibrium. The phase space distribution function, now mapped in unprecedented detail by Gaia, exhibits bending and breathing waves along with intriguing phase space spirals. As with galactic bars, spiral structure, and warps, these phenmena lack a complete and satisfactory explanation. I will describe some of the projects in my group on solar neighborhood dynamics including a study of the vertical potential (the Oort problem) and Gaussian Process model for stellar streaming motions. I will then describe a shearing box calculation that explores the connection between swing amplification and the Gaia phase spirals. The calculation highlights the importance of self-gravitiy in the evolution of the spirals and calls into question simple kinematic models for understanding their origin and evolution.