  The elementary excitations for a BEC trapped by means of an isotropic
harmonic oscillator are studied in the present work. The analysis of these
perturbations is done in the context of the Bogoliubov equations and not
resorting to the hydrodynamic version. The comparison between these two
approaches will allow us to deduce a parameter explaining the role that the
scattering length and the trap play in the way in which the frequency of these
elementary excitations acquires information about the angular momentum of the
corresponding solutions. It will be shown that outside the validity realm of
the Thomas_fermi approximation the frequencies of the perturbations cannot
inherit the information of the angular momentum codified in the functions
escribing the elementary excitations.
