Can someone please explain the following in mathematical language? "First of all, angular excitations only push the energy up, never down, so it is enough to analyze spherically symmetric s-waves...", c.f. first answer in https://physics.stackexchange.com/questions/370901/solution-for-inverse-square-potential-in-d-3-spatial-dimensions-in-quantum-mec
Is that assertion also valid in $N$ dimensions? And more generally for a Schrodinger operator in a rotationally symmetric riemannian manifold with radial potential? In that case, how to prove it? (references are welcome).
In fact, I would like to apply that kind of results in the study of stability of minimal surfaces. More details and context in this related question: Fourier mode decomposition and eigenvalues of Schroedinger operators with radial potential in N-dimensions