Obstacle problems for integro-differential operators: Higher regularity of free boundaries

By Nicola Abatangelo, Xavier Ros-Oton. Advances in Mathematics, 2019

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We study the higher regularity of free boundaries in obstacle problems for integro-differential operators. Our main result establishes that, once free boundaries are $C^{1,\alpha}$, then they are $C^\infty$. This completes the study of regular points, initiated in [5]. In order to achieve this, we need to establish optimal boundary regularity estimates for solutions to linear nonlocal equations in $C^{k,\alpha}$ domains. These new estimates are the core of our paper, and extend previously known results by Grubb (for $k=\infty$) and by the second author and Serra (for $k=1$).

Subfields: Applied Mathematics, Computational Theory and Mathematics

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