Contractive intertwining dilations of quasi-contractions
Summary: We prove that quasi-contractions in Kreĭn spaces always have contractive intertwining dilations. This result covers many of the known lifting of commutant theorems in both Hilbert and Kreĭn spaces. The approach is an adaptation of the angular operator method and uses the existence of invariant maximal non-negative subspaces for certain operators.
existence of invariant maximal non-negative subspaces
scientific article; zbMATH DE number 856804