2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123646In the scattering theory framework, we point out a connection between the spectrum of the scattering matrix of two operators and the spectrum of the difference of spectral projections of these operators.Latex, 14 pagesSpectral Theory47A40 (Primary) 35P25, 47B35 (Secondary)text