We prove weighted analytic regularity of solutions to the Dirichlet problem
for the integral fractional Laplacian in polytopal three-dimensional domains
and with analytic right-hand side. Employing the Caffarelli-Silvestre extension
allows to localize the problem and to decompose the regularity estimates into
results on vertex, edge, face, vertex-edge, vertex-face, edge-face and
vertex-edge-face neighborhoods of the boundary. Using tangential
differentiability of the extended solutions, a bootstrapping argument based on
Caccioppoli inequalities on dyadic decompositions of the neighborhoods provides
control of higher order derivatives.Comment: arXiv admin note: text overlap with arXiv:2112.0815