I'm looking for a formula to interpolate between two given matrices from the Stiefel manifold (orthogonal n by k matrices).
I do not know the tangent direction, I only know the start and end points so I'm not sure if formulas requiring the tangent vector to the Stiefel manifold can be used.
So far, I have looked at the paper by Edelman et al and Huper's "Rolling Stiefel manifolds".
Thanks.