2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/99794We study the relation between the spectrum of a self-adjoint operator and its multidimensional numerical range. It turns out that the multidimensional numerical range is a convex set whose extreme points are sequences of eigenvalues of the operator. Every collection of eigenvalues which can be obtained by the Rayleigh--Ritz formula generates an extreme point of the multidimensional numerical range. However, it may also have other extreme points.35 pagesSpectral Theory47A12, 05C50text