Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2003/iii/paper-16/3/c/solution

Take unit-curvature Real projective space with , and any point . It is complete with positive sectional curvature. A unit-speed geodesic through lifts to
Since 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. Hence
This is cut and conjugate times in round real projective space.

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