Nodal sets and continuity of eigenfunctions of Krein-Feller operators on Riemannian manifolds

Abstract: Let $d\geq1$, $\Omega$ be a bounded domain of a smooth complete Riemannian d-manifold M, and $\mu$ be a positive finite Borel measure with compact support in $\overline{\Omega}$. We prove the Courant nodal domain theorem for the eigenfunctions of Kre\u{i}n-Feller operator $\Delta_{\mu}$ under the assumption that such eigenfunctions are continuous on $\overline{\Omega}$. For $d\geq2$, We prove that on a bounded domain $\Omega\subset M$ with smooth boundary and on which the Green's function of the Laplace-Beltrami operator exists, the eigenfunctions of $\Delta_{\mu}$ are continuous on $\Omega$. We also prove that if M is compact and $\partial M=\emptyset$, then the eigenfuctions of $\Delta_{\mu}$ are continuous on M.