Quantitative comparison results for first-order Hamilton-Jacobi equations
Vincenzo Amato, Luca Barbato
TL;DR
This work addresses the stability of a classical symmetry result for the first-order Hamilton-Jacobi equation $| abla u|=f(x)$ under domain symmetrisation. By coupling rearrangement theory with quantitative inequalities (isoperimetric, Pólya–Szegő, Hardy–Littlewood) and introducing pseudo-rearrangements, the authors prove that the $L^1$ deficit ${\|u^G\|}_1-{\|u\|}_1$ controls both the domain's Fraenkel asymmetry and the distance of $u$ from radial symmetry, yielding a quantitative stability version of the Giarrusso-Nunziante inequality; they also obtain partial control of the source term via a rearrangement $f_u$. The approach hinges on gradient rearrangements, rescaling arguments, and sharp estimates linking asymmetry propagation along level sets to the deficit, culminating in explicit exponents and constants. These results advance shape-optimization analysis for Hamilton-Jacobi equations and provide robust, quantitative measures of how domain geometry and data symmetry influence solutions.
Abstract
In this paper, we study a quantitative refinement of a classical symmetrisation result for first-order Hamilton-Jacobi equations. We prove that the deficit in the comparison result, established by Giarrusso and Nunziante, controls both the asymmetry of the domain and the deviation of the solution and data from radial symmetry. This yields a stability version of the Giarrusso-Nunziante inequality.
