#### Speaker: Trevor Leslie (University of Southern California)

The Euler Alignment system is a hydrodynamic PDE version of the celebrated Cucker-Smale ODE's of collective behavior. Together with Changhui Tan, we developed a theory of weak solutions in 1D, which provide a uniquely determined way to evolve the dynamics after a blowup. Inspired by Brenier and Grenier's work on the pressureless Euler equations, we show that the dynamics of our system are captured by a nonlocal scalar balance law. We generate the unique entropy solution of a discretization of this balance law by introducing the "sticky particle Cucker-Smale" system to track the shock locations. Our approximation scheme for the density converges in the Wasserstein metric; it does so with a quantifiable rate as long as the initial velocity is at least Holder continuous. In this talk, we will discuss the limiting configurations, or "flocking states," that arise in this system, and how to predict them from the initial data.

Time: April 21, 2023 2:30pm-3:30pm

Location: LeConte 440

Host: Changhui Tan