Nodal domain theorems à la Courant. (English) Zbl 1067.35051

Ancona, A.; Helffer, B.; Hoffmann-Ostenhof, T.

Doc. Math. 9, 283-299 (2004).

Authors’ abstract: Let \(H(\Omega_0)=-\Delta+V\) be a Schrödinger operator on a bounded domain \(\Omega_0\subset \mathbb R^d\) (\(d\geq 2\)) with Dirichlet boundary condition. Suppose that \(\Omega_\ell\) (\(\ell \in \;1,\dots,k\)) are some pairwise disjoint subsets of \(\Omega_0\) and that \(H(\Omega_\ell)\) are the corresponding Schrödinger operators again with Dirichlet boundary condition. We investigate the relations between the spectrum of \(H(\Omega_0)\) and the spectra of the \(H(\Omega_\ell)\). In particular, we derive some inequalities for the associated spectral counting functions which can be interpreted as generalizations of Courant’s nodal theorem. For the case where equality is achieved we prove converse results. In particular, we use potential theoretic methods to relate the \(\Omega_\ell\) to the nodal domains of some eigenfunction of \(H(\Omega_0)\).

Reviewer: Mihai Pascu (Bucureşti)

MSC:

35P05	General topics in linear spectral theory for PDEs
35J10	Schrödinger operator, Schrödinger equation
35B05	Oscillation, zeros of solutions, mean value theorems, etc. in context of PDEs
31C15	Potentials and capacities on other spaces

Keywords:

Schrödinger operator; Dirichlet boundary conditions; spectral counting functions; nodal domains; capacity