La méthode de la fonction génératrice et les développements en quasibosons

An isomorphism between the oH' subspace of the physical bound states and a normalized oF functional space is established. This is done by introducing a generating function for these oH' states. By choosing for the oH-space the Bargmann's space, an isomorphism is obtained between an oH_F space of the fermion states and an oH_B space of the boson states. An expansion of any quasiboson operator of oH_B is thus feasible. This is particularly interesting for the Hamiltonian operator. In this case the expansion obtained, similar to the Beliaev-ZeIevinski and Marumori expansions, appear to be simple and more convergent.