Pinsky Lecture Series

Title: Flows of nonsmooth vector fields
Speaker: Camillo De Lellis
Speaker Info: Institute of Advanced Study
Brief Description:
Special Note:

Consider a vector field $v$ on the Euclidean space. The classical Cauchy-Lipschitz (also named Picard-Lindelöf) Theorem states that, if the vector field is Lipschitz in space, for every initial datum $x$ there is a unique trajectory $\gamma$ starting at $x$ at time $0$ and solving the ODE $\dot \gamma (t) = v (t, \gamma (t))$. The theorem loses its validity as soon as v is slightly less regular. However, if we bundle all trajectories into a global map allowing $x$ to vary, a celebrated theory started by DiPerna and Lions in the 80's shows that there is a unique such flow under very reasonable conditions and for much less regular vector fields. This theory has a lot of repercussions to several important partial differential equations where the idea of "following the trajectories of particles" plays a fundamental role.

In these three lectures I will review the state of the art of the subject, touching upon a variety of related topics, such as the most recent surprising outcomes of convex-integration techniques and the most interesting applications to evolutionary PDEs.

This is the second of the three lectures.

Date: Thursday, April 13, 2023
Time: 04:00pm
Where: Lunt 105
Contact Person: Ben Weinkove
Contact email: weinkove@math.northwestern.edu
Contact Phone:
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