Higher order terms for the quantum evolution of a Wick observable within the Hepp method

the hepp method is the coherent state approach to the mean field dynamics for bosons or to the semiclassical propagation. a key point is the asymptotic evolution of wick observables under the evolution given by a time-dependent quadratic hamiltonian. this article provides a complete expansion with respect to the small parameter which makes sense within the infinite-dimensional setting and fits with finite-dimensional formulae.