2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/225952The unbounded bicommutant $(\mathfrak M_{E'})''$ of the {\em reduction} of an O*-algebra $\MM$ via a given projection $E'$ weakly commuting with $\mathfrak M$ is studied, with the aim of finding conditions under which the reduction of a GW*-algebra is a GW*-algebra itself. The obtained results are applied to the problem of the existence of conditional expectations on O*-algebras.Proc. of the Amer. Math. Soc., in pressMathematical Physicstext