Generic regularity of free boundaries for the obstacle problem

The goal of this paper is to establish generic regularity of free boundaries for the obstacle problem in $\mathbb{R}^n$. By classical results of Caffarelli, the free boundary is $C^{\infty}$ outside a set of singular points. Explicit examples show that the singular set could be in general $(n-1)$-di...

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Detalles Bibliográficos
Autores: Figalli, Alessio, Ros, Xavier, Serra Montolí, Joaquim
Tipo de recurso: artículo
Estado:Versión aceptada para publicación
Fecha de publicación:2020
País:España
Institución:Universidad de Barcelona
Repositorio:Dipòsit Digital de la UB
OAI Identifier:oai:diposit.ub.edu:2445/194135
Acceso en línea:https://hdl.handle.net/2445/194135
Access Level:acceso abierto
Palabra clave:Problemes de contorn
Equacions en derivades parcials
Funcions de variables complexes
Distribució (Teoria de la probabilitat)
Boundary value problems
Partial differential equations
Functions of complex variables
Distribution (Probability theory)
Descripción
Sumario:The goal of this paper is to establish generic regularity of free boundaries for the obstacle problem in $\mathbb{R}^n$. By classical results of Caffarelli, the free boundary is $C^{\infty}$ outside a set of singular points. Explicit examples show that the singular set could be in general $(n-1)$-dimensional - that is, as large as the regular set. Our main result establishes that, generically, the singular set has zero $\mathcal{H}^{n-4}$ measure (in particular, it has codimension 3 inside the free boundary). In particular, for $n \leq 4$, the free boundary is generically a $C^{\infty}$ manifold. This solves a conjecture of Schaeffer (dating back to 1974 ) on the generic regularity of free boundaries in dimensions $n \leq 4$