2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/144784We give a new proof of a result of Ozawa showing that if a von Neumann subalgebra $Q$ of a free group factor $L\Bbb F_n, 2\leq n\leq \infty$ has relative commutant diffuse (i.e. without atoms), then $Q$ is amenable.Final form; paper appeared in Int. Math. Res. Notices, 2007Operator Algebras46L10text