Period doubling bifurcations and universality in conservative systems

We have studied numerically a sequence of period doubling bifurcations of periodic orbits of Hénon's conservative two-dimensional mapping. In agreement with other recent studies, we also find evidence that such sequences possess universality properties, similar to the ones observed for dissipative systems. The corresponding universal constants, however, have significantly different values in each case. We suggest that a possible explanation for this discrepancy may be the fact that conservative systems, owing to their measure preserving property, do not become asymptotically one-dimensional, as dissipative systems do.