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Journal of the European Mathematical Society


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Volume 12, Issue 5, 2010, pp. 1151–1179
DOI: 10.4171/JEMS/226

Published online: 2010-08-15

Variational problems with free boundaries for the fractional Laplacian

Luis A. Caffarelli[1], Jean-Michel Roquejoffre[2] and Yannick Sire[3]

(1) University of Texas at Austin, USA
(2) Université Paul Sabatier, Toulouse, France
(3) Université Aix-Marseille, Marseille, France

We discuss properties (optimal regularity, non-degeneracy, smoothness of the free boundary...) of a variational interface problem involving the fractional Laplacian; Due to the non-locality of the Dirichlet problem, the task is nontrivial. This difficulty is by-passed by an extension formula, discovered by the first author and Silvestre, which reduces the study to that of a co-dimension 2 (degenerate) free boundary.

Keywords: Fractional Laplacian, free boundary

Caffarelli Luis, Roquejoffre Jean-Michel, Sire Yannick: Variational problems with free boundaries for the fractional Laplacian. J. Eur. Math. Soc. 12 (2010), 1151-1179. doi: 10.4171/JEMS/226