### Congratulations to Dr. Tan!

Dr. Changhui Tan awarded an NSF CAREER grant for the project, ``Nonlocal partial differential equations in collective dynamics and fluid flow” from the Division of Mathematical Sciences. Considered one of the National Science Foundation's most prestigious awards, this grant supports early-career faculty in both their research and educational missions.

This is only the second such award in our program’s history, the first award was to Paula Vasquez in 2018.

Abstract of Award: The collective behaviors of large groups of similar animals, e.g.,
birds, insects, or fishes, are ubiquitous in nature. In recent times, the mathematical
study of collective dynamics has become an active and fast-growing field of research.
Many mathematical models of collective behavior rely on partial differential equations
with nonlocal interactions to describe the resulting emergent behavior. It turns out
that these models are intimately connected to other models traditionally used in fluid
dynamics. The goal of this project is to study several models of nonlocal partial
differential equations to model collective behavior or fluid flows, and to develop
novel and robust analytical techniques to understand the collective behaviors driven
by nonlocal structures. The training and professional development of graduate students
and young researchers is an integral part of the project.

This project studies three families of partial differential equations with shared
nonlocal structures that can affect the solutions of the equations: existence, uniqueness,
regularity, and long-time asymptotic behaviors. The first problem is on the compressible
Euler system with nonlinear velocity alignment, which describes the remarkable flocking
phenomenon in animal swarms. Global phenomena and asymptotic behaviors of the system
will be investigated, with a focus on the nonlinearity in the velocity alignment.
The second problem is on the pressure-less Euler system, aiming at the long-standing
question of the uniqueness of weak solutions. The plan is to approximate the system
by the relatively well-studied Euler-alignment system in collective dynamics. The
third problem is on the Euler-Monge-Ampère system which is closely related to the
incompressible Euler equations in fluid dynamics. The embedded nonlocal geometric
structure of the system will be explored, with interesting applications in optimal
transport and mean-field games.

View Dr. Tan's Website here and the NSF grant information here.