Disjointly universal inner functions
arXiv:2606.19225
Abstract
We characterize when two sequences of composition operators admit disjointly universal Blaschke products and singular inner functions. The characterizations we provide depend on geometric features of the symbols like their hyperbolic derivatives and pseudo hyperbolic distances. To achieve our results, we build a disjoint universality criterion for sequences of maps that act on a metrizable, complete topological semigroup.