Vectorial variational problems in $L^{\infty }$ constrained by the Navier-Stokes equations

Abstract

We study a minimisation problem in $L^p$ and $L^{\infty }$ for certain cost functionals, where the class of admissible mappings is constrained by the Navier-Stokes equations. Problems of this type are motivated by variational data assimilation for atmospheric flows arising in weather forecasting. Herein we establish the existence of PDE-constrained minimisers for all $p$, and also that $L^p$ minimisers converge to $L^{\infty }$ minimisers as $p\to \infty$. We further show that $L^p$ minimisers solve an Euler-Lagrange system. Finally, all special $L^{\infty }$ minimisers constructed via approximation by $L^p$ minimisers are shown to solve a divergence PDE system involving measure coefficients, which is a divergence-form counterpart of the corresponding non-divergence Aronsson-Euler system.

21 pages, Journal: Nonlinearity (accepted)