Efficient Quasi-Geodesics on the Stiefel Manifold

Solving the so-called geodesic endpoint problem, i.e., finding a that connects two given points on manifold, is at basis of virtually all data processing operations, including averaging, clustering, interpolation and optimization. On Stiefel manifold orthonormal frames, this problem computationally involved. A remedy to use quasi-geodesics as replacement for Riemannian geodesics. Quasi-geodesics feature constant speed covariant acceleration with (but possibly non-zero) norm. For well-known type quasi-geodesics, we derive new representation suited large-scale computations. Moreover, introduce kind turns out be much closer