  We study Bose-Einstein condensate of atomic Boson gases trapped in a
composite potential of a harmonic potential and an optical lattice potential.
We found a series of collective excitations that induces localized vortex
oscillations with a characteristic wavelength. The oscillations might be
observed experimentally when radial confinement is tight. We present the
excitation spectra of the vortex oscillation modes and propose a way to
experimentally excite the modes.
