Abstract
In this paper the stability of standard a accretion disks against perturbations in the radial direction is taken in the light of linear perturbation theory. This analysis starts from slightly different, but correct, continuity and momentum equations, besides imposing null boundary conditions on the perturbations and continuity along the flow. With such a treatment, we do obtain more stable disks, to some modifications in the results earlier obtained by Shakura and Sunyaev (1975).
