Approximation properties for free orthogonal and free unitary quantum groups

Abstract: We show that the reduced von Neumann algebras of the free orthogonal and free unitary quantum groups have the Haagerup approximation property. Using this result and a Haagerup-type inequality for these quantum groups due to Vergnioux (J. Operator Theory 57, 303-324 (2007)), we also show that the reduced C$^\ast$-algebras of the free orthogonal and free unitary quantum groups have the metric approximation property.