2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16385We study the mechanical stability of the weakly interacting Bose gas with attractive interactions, and construct a unified picture of the collapse valid from the low temperature condensed regime to the high temperature classical regime. As we show, the non-condensed particles play a crucial role in determining the region of stability, even providing a mechanism for collapse in the non-condensed cloud. Furthermore, we demonstrate that the mechanical instability prevents BCS-type ``pairing'' in the attractive Bose gas. We extend our results to describe domain formation in spinor condensates.23 pages, 5 figures -- expanded version of cond-mat/9908133Statistical MechanicsSoft Condensed Mattertext