I know there is a notion of principal angles between subpaces of a Euclidean space, but what about subspaces of a finite dimensional vector space $V$ equipped with a non-degenerate quadratic form of indefinite signature ?
A first approach would be to define the angle $(V_1,V_2)$ to be the class of all pseudo-orthogonal transformations sending $V_1$ to $V_2$ and then to parametrize this class in terms of real numbers. Of course this is limited to subspaces having the same dimension and on which the quadratic form has the same signature.
Is anybody aware of some research along these lines ?
