Konwersatorium im. Leopolda Infelda

A dilute Bose gas of neutral atoms was condensed in 1995. The experiments and the theory hasachieved a lot since the first experiment. The theoretical description of the ultra cold Bose atnonzero temperatures is still a challenge. More than a decade ago we have formulated a relativelysimple method of describing properties and processes involving such a gas. I will explain thisapproximate methods and present its several successful applications.