The APDE seminar on Monday, 10/31, will be given by Frédéric Klopp (Sorbonne U & UC Berkeley) in-person in Evans 740, and will also be broadcasted online via Zoom from 4:10pm to 5:00pm PST. To participate, email Sung-Jin Oh ().

Title: A complex WKB analysis for finite difference Schrödinger operators and adiabatic perturbations of periodic Schrödinger operators

Abstract: I will explain the basic ideas and constructions of the methods underlining the similarities between the two classes of equations.

The APDE seminar on Monday, 10/17, will be given by Sanchit Chaturvedi (Stanford) in-person in Evans 740, and will also be broadcasted online via Zoom from 4:10pm to 5:00pm PST. To participate, email Sung-Jin Oh ().

Title: Vanishing viscosity and shock formation in Burgers equation

Abstract: I will talk about the shock formation problem for 1D Burgers equation in the presence of small viscosity. Although the vanishing viscosity problem till moments before the first shock and in presence of a fully developed shocks is very classical, little is known about the moment of shock formation. We develop a matched asymptotic expansion to describe the solution to the viscous Burgers equation (with small viscosity) to arbitrary order up to the first singularity time. The main feature of the work is the inner expansion that accommodates the viscous effects close to the shock location and match it to the usual outer expansion (in viscosity). We do not use the Cole-Hopf transform and hence we believe that this approach works for more general scalar 1D conservation laws. Time permitting, I will talk about generalizing to vanishing viscosity limit from compressible Navier–Stokes to compressible Euler equations. This is joint work with Cole Graham (Brown university).