On the nodal domain count under metric perturbations, Courant sharpness and boundary intersections

Abstract: In this note, we investigate the effects of metric perturbations of closed surfaces on the number of nodal domains. In particular, we show that the nodal domain count for Laplace eigenfunctions is (locally) maximised for non-generic metrics. We also investigate localised perturbations and showcase some interesting applications regarding Courant sharp metrics on closed surfaces and associated boundary nodal-data prescription problems.