2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/27481We present a unified picture of the interaction effects in dilute atomic quantum gases. We consider fermionic as well as bosonic gases and, in particular, discuss for both forms of statistics the fundamental differences between a gas with effectively repulsive and a gas with effectively attractive interatomic interactions, i.e.\ between a gas with either a positive or a negative scattering length.Invited paper for the NIST Journal of ResearchCondensed Mattertext