Spectral Obstructions to Contracting Transport Maps on Curved Spaces

Abstract

Caffarelli's contraction theorem states that the Brenier optimal transport map from the standard Gaussian measure to a more log-concave probability measure is 1-Lipschitz. Owing to its many applications in analysis, probability, and geometry, the problem of extending this theorem to curved spaces has appeared repeatedly in the literature, going back to Villani [V09]. More recently, Milman [Mil18] formulated precise conjectures in this direction. In this work, we construct counterexamples to these conjectures.