Abstract. We study the relative position of three subspaces in an infinite-dimensional Hilbert space. In the finite-dimensional case over an arbitrary field, Brenner described the general position of three subspaces completely. We extend it to a certain class of three subspaces in an infinite-dimensional Hilbert space over the complex numbers.
AMS Subject Classification
(1991): 46C07, 47A15, 15A21, 16G20, 16G60
Received August 6, 2018 and in final form November 25, 2018. (Registered under 71/2018.)