Narrow Results

We prove that discrete compact quantum groups (or more generally locally compact, under additional hypotheses) with coamenable dual are continuous fields over their central closed quantum subgroups, and the same holds for free products of discrete quantum groups with coamenable dual amalgamated over a common central subgroup. Along the way we also show that free products of continuous fields of $C^{\ast }$-algebras are again free via a Fell-topology characterization for $C^{\ast }$-field continuity, recovering a result of Blanchard’s in a somewhat more general setting.

We characterize the pairs of closed homomorphisms and closed quomorphisms of partial Σ-algebras that have a pushout in the corresponding category, for an arbitrary signature Σ. The latter characterization solves the basic problem previous to the development of a single-pushout approach to the transformation of partial algebras based on closed quomorphisms.