We provide counterexamples to regularity of optimal maps in the classical Monge problem under various assumptions on the initial data. Our construction is based on a variant of the counterexample in [10] to Lipschitz regularity of the monotone optimal map between smooth densities supported on convex domains.
Katrin Beyer, Corentin Jean Dominique Fivet, Stefana Parascho, Qianqing Wang, Maxence Grangeot