2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/76499The norm of an integral operator occurring in the partial wave decomposition of an operator B introduced by Brown and Ravenhall in a model for relativistic one-electron atoms is determined. The result implies that B is non-negative and has no eigenvalue at 0 when the nuclear charge does not exceed a specified critical value.14 pagesSpectral Theory47G, 81Q10, 47N50text