  We study the problem of causal structure learning from data using optimal
transport (OT). Specifically, we first provide a constraint-based method which
builds upon lower-triangular monotone parametric transport maps to design
conditional independence tests which are agnostic to the noise distribution. We
provide an algorithm for causal discovery up to Markov Equivalence with no
assumptions on the structural equations/noise distributions, which allows for
settings with latent variables. Our approach also extends to score-based causal
discovery by providing a novel means for defining scores. This allows us to
uniquely recover the causal graph under additional identifiability and
structural assumptions, such as additive noise or post-nonlinear models. We
provide experimental results to compare the proposed approach with the state of
the art on both synthetic and real-world datasets.
