It was pointed out by Y. Eliashberg in his ICM 2006 plenary talk that the
rich algebraic formalism of symplectic field theory leads to a natural
appearance of quantum and classical integrable systems, at least in the case
when the contact manifold is the prequantization space of a symplectic
manifold. In this paper we generalize the definition of gravitational
descendants in SFT from circle bundles in the Morse-Bott case to general
contact manifolds. After we have shown that for the basic examples of
holomorphic curves in SFT, that is, branched covers of cylinders over closed
Reeb orbits, the gravitational descendants have a geometric interpretation in
terms of branching conditions, we compute the corresponding sequences of
Poisson-commuting functions when the contact manifold is the unit cotangent
bundle of a Riemannian manifold.Comment: 44 pages, no figure