2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/127859A new variant of the Feshbach map, called smooth Feshbach map, has been introduced recently by Bach et al., in connection with the renormalization analysis of non-relativistic quantum electrodynamics. We analyze and clarify its algebraic and analytic properties, and we generalize it to non-selfadjoint partition operators $χ$ and $\chib$.8 pagesMathematical PhysicsFunctional Analysis47A05, 81Q10text