This was part of
Emergent Behavior in Complex Systems of Interacting Agents
Existence and long time behavior of weak solutions to the Fokker-Planck-Alignment models
Roman Shvydkoy, University of Illinois at Chicago
Monday, March 17, 2025
Abstract: In this talk we address global existence of weak solutions, their regularization, and global relaxation to Maxwellian for a broad class of Fokker-Planck-Alignment models which appear in collective dynamics. The main feature of these results, as opposed to previously known ones, is the lack of regularity or no-vacuum requirements on the initial data. With a particular application to the classical kinetic Cucker-Smale model, we demonstrate that any bounded data with finite energy, $(1+ |v|^2) f_0 in L^1, f_0 in L^infty$, and finite higher moment $|v|^q f in L^2$, $q gg 2$, gives rise to a global instantly smooth solution, satisfying entropy equality and relaxing exponentially fast.
The results are achieved through the use of a new thickness-based renormalization, which circumvents the problem of degenerate diffusion in non-perturbative regime.