Past exam of the mathematics course of the University of Cambridge 2003 iii Paper 16 3 c Solution Created 2026-10-03 Updated 2026-10-14
Take unit-curvature Real projective space with , and any point . It is complete with positive sectional curvature. A unit-speed geodesic through lifts toSince the two representatives of an endpoint are antipodal, Riemannian distance in the quotient is the smaller of the two spherical distances:This equals for and is strictly smaller just afterwards. Thus the Riemannian cut point occurs at time in every direction.
Along a curvature-one geodesic, every normal Jacobi field with initial value zero is , where is parallel transport and . Its first further zero is . The quotient map is a local isometry, so the Jacobi field equation and conjugacy times are unchanged. HenceThis is cut and conjugate times in round real projective space.