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Towards the smoothness of optimal maps on Riemannian submersions and Riemannian products (of round spheres in particular)

  • Young-Heon Kim EMAIL logo and Robert J. McCann
Published/Copyright: June 28, 2011

Abstract

The variant A3w of Ma, Trudinger and Wang's condition for regularity of optimal transportation maps is implied by the non-negativity of a pseudo-Riemannian curvature—which we call cross-curvature—induced by the transportation cost. For the Riemannian distance squared cost, it is shown that (1) cross-curvature non-negativity is preserved for products of two manifolds; (2) both A3w and cross-curvature non-negativity are inherited by Riemannian submersions, as is domain convexity for the exponential maps; and (3) the n-dimensional round sphere satisfies cross-curvature non-negativity. From these results, a large new class of Riemannian manifolds satisfying cross-curvature non-negativity (thus A3w) is obtained, including many whose sectional curvature is far from constant. All known obstructions to the regularity of optimal maps are absent from these manifolds, making them a class for which it is natural to conjecture that regularity holds. This conjecture is confirmed for certain Riemannian submersions of the sphere such as the complex projective spaces ℂℙn.

Received: 2009-02-02
Revised: 2009-11-19
Published Online: 2011-06-28
Published in Print: 2012-03

©[2012] by Walter de Gruyter Berlin Boston

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