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# Applied Math Seminar — Illia Karabash (IAMM of NAS of Ukraine and TU Dortmund)

## February 28, 2022 @ 4:15 pm - 5:15 pm

Title: Pareto optimization of resonances and optimal control methods

Abstract:

First successes in fabrication of high-Q optical cavities two decades ago led to active applied physics and numerical studies of optimization problems involving resonances. The questions is how to design an open resonator that has an eigenvalue as close as possible to the real line under certain constraints. The analytic spectral optimization theory for such types of non-Hermitian eigenproblems is still in the stage of development. It is planned to explain briefly why the Pareto optimization settings are natural for non-Hermitian spectral problems, and how the associated nonlinear Euler-Lagrange eigenproblems can be rigorously derived for the case of resonances in 1-d photonic crystals. Then we concentrate on the recently developed optimal control approach of (Karabash, Koch, Verbytskyi `20) and show how it is related to Pareto frontiers and Hamilton-Jacobi-Bellman PDEs. An application of Pontryagin Maximum Principle and a special method of minimum-time shooting to a line of no-return will be also discussed.