Optimal Domains for Elliptic Eigenvalue Problems with Rough Coefficients
Stanley Snelson, Eduardo V. O. Teixeira · SIAM Journal on Mathematical Analysis · 2024
Abstract. We prove the existence of an open set minimizing the first Dirichlet eigenvalue of an elliptic operator with bounded, measurable coefficients, over all open sets of a given measure. Our proof is based on a free boundary approach: we characterize the eigenfunction on the optimal set as the minimizer of a penalized functional, and derive openness of the optimal set as a consequence of a Hölder estimate for the eigenfunction. We also prove that the optimal eigenfunction grows at most linearly from the free boundary, i.e., it is Lipschitz continuous at free boundary points.