# Boundedness of the number of nodal domains for eigenfunctions of generic Kaluza-Klein $3$-folds

Research paper by Junehyuk Jung, Steve Zelditch

Indexed on: 12 Jun '18Published on: 12 Jun '18Published in: arXiv - Mathematics - Spectral Theory

#### Abstract

This article concerns the number of nodal domains of eigenfunctions of the Laplacian on special Riemannian $3$-manifolds, namely nontrivial principal $S^1$ bundles $P \to X$ over Riemann surfaces equipped with certain $S^1$ invariant metrics, the Kaluza-Klein metrics. We prove for generic Kaluza-Klein metrics that any Laplacian eigenfunction has exactly two nodal domains unless it is invariant under the $S^1$ action. We also construct an explicit orthonormal eigenbasis on the flat $3$-torus $\mathbb{T}^3$ for which every non-constant eigenfunction belonging to the basis has two nodal domains.