  It has been suggested that quasi-periodic oscillations of accreting X-ray
sources may relate to the modes named in the title. We consider
non-axisymmetric linear perturbations to an isentropic, isothermal,
unmagnetized thin accretion disk. The radial wave equation, in which the number
of vertical nodes (n) appears as a separation constant, admits a wave-action
current that is conserved except, in some cases, at corotation. Waves without
vertical nodes amplify when reflected by a barrier near corotation. Their
action is conserved. As was previously known, this amplification allows the n=0
modes to be unstable under appropriate boundary conditions. In contrast, we
find that waves with n >0 are strongly absorbed at corotation rather than
amplified; their action is not conserved. Therefore, non-axisymmetric p-modes
and g-modes with n>0 are damped and stable even in an inviscid disk. This
eliminates a promising explanation for quasi-periodic oscillations in
neutron-star and black-hole X-ray binaries.
