Structure and regularity of the singular set in the obstacle problem for the fractional Laplacian

We study the singular part of the free boundary in the obstacle problem for the fractional Laplacian, $\min \left\{(-\Delta)^s u, u-\varphi\right\}=0$ in $\mathbb{R}^n$, for general obstacles $\varphi$. Our main result establishes the complete structure and regularity of the singular set. To prove i...

Full description

Bibliographic Details
Authors: Garofalo, Nicola, Ros, Xavier
Format: article
Status:Versión aceptada para publicación
Publication Date:2019
Country:España
Institution:Universidad de Barcelona
Repository:Dipòsit Digital de la UB
OAI Identifier:oai:diposit.ub.edu:2445/194048
Online Access:https://hdl.handle.net/2445/194048
Access Level:Open access
Keyword:Operadors diferencials parcials
Teoria d'operadors
Equacions en derivades parcials
Processos estocàstics
Partial differential operators
Operator theory
Partial differential equations
Stochastic processes
Description
Summary:We study the singular part of the free boundary in the obstacle problem for the fractional Laplacian, $\min \left\{(-\Delta)^s u, u-\varphi\right\}=0$ in $\mathbb{R}^n$, for general obstacles $\varphi$. Our main result establishes the complete structure and regularity of the singular set. To prove it, we construct new monotonicity formulas of Monneau-type that extend those in those of Garofalo-Petrosyan to all $s \in(0,1)$.