STABILITY AND COLLECTIVE EXCITATIONS OF A 2-COMPONENT BOSE-EINSTEIN CONDENSED GAS - A MOMENT APPROACH

The dynamics of a two-component dilute Bose-Einstein gas of atoms at z ero temperature is described in the mean-field approximation by a two- component Gross-Pitaevskii equation. We solve this equation assuming a Gaussian shape for the wave function, where the free parameters of th e trial wave function are determined using a moment method, We derive equilibrium states and the phase diagrams for the stability for positi ve and negative s-wave scattering lengths, and obtain the low-energy e xcitation frequencies corresponding to the collective; motion of the t wo Bose-Einstein condensates.