|Dept.||Shanghai Normal University|
Halmos two projections theorem for Hilbert space operators is one of the fundamental results in operator theory. In this talk we will focus on its generalization to the Hilbert C*-module case, and its application in clarifying the Friedrichs angle between two closed submodules. Based on some new characterizations of the closed submodules and their associated projections, we will introduce a new term of separated idempotents. Some properties of the seperated idempotents will be presented.