Quasi-Periodic Oscillations in Relativistic Tori
  Motivated by recent interesting work on p-mode oscillations in axisymmetric hydrodynamic black-hole tori by Rezzolla, Zanotti, and collaborators, I explore the robustness of these oscillations by means of two and three-dimensional relativistic hydrodynamic and MHD simulations. The primary purpose of this investigation is to determine how the amplitudes of these oscillations are affected by the presence of known instabilities of black-hole tori, including the Papaloizou-Pringle instability (PPI) and the magneto-rotational instability (MRI). Both instabilities drive accretion at rates above those considered in Rezzolla's work. The increased accretion can allow wave energy to leak out of the torus into the hole. Furthermore, with the MRI, the presence of turbulence, which is absent in the hydrodynamic simulations, can lead to turbulent damping (or excitation) of modes. The current numerical results are preliminary, but suggest that the PPI and MRI both significantly damp acoustic oscillations in tori. 
P. Chris Fragile (UC Santa Barbara)