The Disintegration of the Lebesgue Measure on the Faces of a Convex Function

We consider the disintegration of the Lebesgue measure on the graph of a convex function w.r.t. the partition into its faces, which are convex sets and therefore have a well defined linear dimension, and we prove that each conditional measure is equivalent to the k-dimensional Hausdorff measure on the k-dimensional face on which it is concentrated. The remarkable fact is that a priori the directions of the faces are just Borel and no Lipschitz regularity is known. Notwithstanding that, we also prove that a Green–Gauss formula for these directions holds on special sets.