A Faber-Krahn inequality for the Riesz potential operator for triangles and quadrilaterals (Q2078951)

In this paper, the authors proved an analog of the Faber-Krahn inequality for the Riesz potentialoperator. The proof was based on Riesz's inequality under Steiner symmetrization and the continuity of the first eigenvalue of the Riesz potential operator with respect to the convergence, in the complementary Hausdorff distance, of a family of uniformly bounded non-empty convex open sets.