Uniqueness results of a nonlinear stochastic diffusion-convection equation with reflection
Niklas Sapountzoglou
TL;DR
This work analyzes the uniqueness of solutions to a nonlinear stochastic diffusion-convection obstacle problem with reflection on a bounded Lipschitz domain under additive noise. The authors develop contraction-type results for regular solutions, obtaining a pathwise $L^2$-contraction when the operator $a$ is independent of the second argument and an $L^1$-contraction in the general case via a smoothing argument using $n_{\delta}$, while highlighting the limitations imposed by the lack of a general It\ô formula in higher dimensions. They further discuss regularization-based strategies and the need for extra space-time regularity to extend these results, showing that full uniqueness in the rough regime remains open. The appendix establishes cap$_p$-based quasi-continuity tools to handle the reflection measure and the obstacle constraint rigorously, providing a solid analytic foundation for the stochastic obstacle problem framework.
Abstract
We are interested in the uniqueness of solutions of a nonlinear, pseudomonotone, stochastic diffusion evolution problem with homogeneous Dirichlet boundary conditions with reflection, where the noise term is additive and given by a stochastic Itô integral with respect to a Hilbert space valued cylindrical Wiener process. In fact, since there is no Itô formula available for a solution in general, a general uniqueness result seems not to be available. Nevertheless, assuming more regularity for the solutions or the reflection, we may show some comparison principles.
