Overdetermined problems with sign-changing eigenfunctions in unbounded periodic domains

Abstract: We prove the existence of nontrivial unbounded domains $\O$ in the Euclidean space $\R^d$ for which the Dirichlet eigenvalue problem for the Laplacian on $\Omega$ admits sign-changing eigenfunctions with constant Neumann values on $\partial \Omega$. We also establish a similar result by studying a partially overdetermined problem on domains with two boundary components and opposite Neumann boundary values. The domains we construct are periodic in some variables and radial in the other variables, and they bifurcate from straight (generalized) cylinder or slab.