2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/69666Motivated by the remarkable interplay between (chordal) graphs and matrix algebra, we associate to each graph a so-called completion number that might encode some aspects of that interplay. We show that this number is not trivial, and we ask for a graph theoretic characterization of those graphs with a given completion number.6 pagesCombinatoricsFunctional Analysistext