On orthogonal systems, two-sided bases and regular subfactors
arXiv:1904.05612
Abstract
We prove that a regular subfator of type with finite Jones index always admits a two-sided Pimsner-Popa basis. This is preceeded by a pragmatic revisit of Popa's notion of orthogonal systems.
15 pages; Theorem 3.12 and few remarks added, feedback is welcome!