LOW-LYING EXCITATIONS OF DOUBLE BOSE-EINSTEIN CONDENSATES

We present the excitation spectrum of a double Bose-Einstein condensat e for the JILA time orbiting potential trap including the effects of g ravity. We consider two cases: (i) fixed scattering lengths and equal numbers of each atomic species as a function of the number of atoms an d (ii) fixed intraspecies scattering lengths and a fixed, equal number of atoms in each state as a function of interspecies scattering lengt h. The spectra reveal the rich dynamics of the system and in particula r show simultaneous collective excitations of both condensates. [S1050 -2947(98)06302-1].