Aggregation Diffusion Equations: Dynamics, Asymptotics, and Singular Limits
Given a large ensemble of interacting particles, driven by nonlocal interactions and localized repulsion, the mean field limit leads to a class of nonlocal, nonlinear partial differential equations known as aggregation diffusion equations. Over the past 15 years, aggregation diffusion equations have become widespread in biological applications and have also attracted significant mathematical interest, due to their competing forces at different length scales. These competing forces lead to rich dynamics, including symmetrization, stabilization, and metastability, as well as sharp dichotomies separating well posedness from finite time blow up. In the present work, we review known analytical results for aggregation diffusion equations and consider singular limits of these equations, including the slow diffusion limit, which leads to the constrained aggregation equation, and localized aggregation and vanishing diffusion limits, which lead to metastability behavior. We also review the range of numerical methods available for simulating solutions, with special attention devoted to recent advances in deterministic particle methods. We close by applying such a method the blob method for diffusion to showcase key properties of the dynamics of aggregation diffusion equations and related singular limits.