Maps on the 𝑛-dimensional subspaces of a Hilbert space preserving principal angles
Lajos Molnár · Proceedings of the American Mathematical Society · 2008
In a former paper we studied transformations on the set of all n n -dimensional subspaces of a Hilbert space H H which preserve the principal angles. In the case when dim H ≠ 2 n \dim H eq 2n , we could determine the general form of all such maps. The aim of this paper is to complete our result by considering the problem in the remaining case dim H = 2 n \dim H=2n .