  We present a detailed temporal analysis of a set of hydrodynamic and
magnetohydrodynamic (MHD) simulations of geometrically-thin (h/r~0.05) black
hole accretion disks. The black hole potential is approximated by the
Paczynski-Wiita pseudo-Newtonian potential. In particular, we use our
simulations to critically assess two widely discussed models for high-frequency
quasi-periodic oscillations, global oscillation modes (diskoseismology) and
parametric resonance instabilities. We find that initially disturbed
hydrodynamic disks clearly display the trapped global g-mode oscillation
predicted by linear perturbation theory. In contrast, the sustained turbulence
produced in the simulated MHD disks by the magneto-rotational instability does
not excite these trapped g-modes. We cannot say at present whether the MHD
turbulence actively damps the hydrodynamic g-mode. Our simulated MHD disks also
fail to display any indications of a parametric resonance instability between
the vertical and radial epicyclic frequencies. On the other hand, we do see
characteristic frequencies at any given radius in the disk corresponding to
local acoustic waves. We also conduct a blind search for any quasi-periodic
oscillation in a proxy lightcurve based on the instantaneous mass accretion
rate of the black hole, and place an upper limit of 2% on the total power in
any such feature. We highlight the importance of correcting for secular changes
in the simulated accretion disk when performing temporal analyses.
