  We study the set of quantum correlations generated by actions on maximally
entangled states. We show that such correlations are dense in their own convex
hull. As a consequence, we show that these correlations are dense in the set of
synchronous quantum correlations. We introduce the concept of corners of
correlation sets and show that every local or nonsignalling correlation can be
realized as the corner of a synchronous local or nonsignalling correlation. We
provide partial results for other correlation sets.
