2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/172028In two languages, Linear Algebra and Lie Algebra, we describe the results of Kostant and Wallach on the fibre of matrices with prescribed eigenvalues of all leading principal submatrices. In addition, we present a brief introduction to basic notions in Algebraic Geometry, Integrable Systems, and Lie Algebra aimed at specialists in Linear Algebra.27 pages, LaTeX; abstract addedSymplectic GeometryRings and Algebrastext