E. Minguzzi, "Clocks' synchronization without round-trip conditions," http://arxiv.org/abs/1009.3005 abstract: "Poincare-Einstein's synchronization convention is transitive, and thus leads to a e consistent synchronization, only if some form of round-trip property is satisfied. An improved version is given here which does not suffer from this limitation and which therefore may find application in physics, computer science and com- munications theory. As for the application to physics, the round-trip condition required by the Poincare-Einstein's synchronization convention corresponds to e a vanishing Sagnac effect and thus to the selection of an irrotational frame. The corrected method applies also to rotating frames and shows that there is a consistent synchronization for every given measure on space. The correction to Poincare-Einstein's amounts to an average of the Sagnac holonomy over all the possible triangular paths. The mathematics used is reminiscent of Alexander cohomology theory." from the conclusions: "Perhaps the most significant consequence is that, contrary to what could be expected, there is, in many cases, a natural splitting of spacetime into space and time and that this result is exact (provided the assumptions are satisfied). This surprising fact may prove to be useful in quantum gravity, where the lack of such a privileged splitting has come to be known as "the problem of time"."