The Radial-Azimuthal Instability of a Radiation-Pressure-Dominated Accretion Disk with Advection*

A radial-azimuthal instability analysis of a radiation-pressure-dominated accretion disk with advection is presented. We find that the including of a very little advection has significant effect on two acoustic modes, which are no longer complex conjugates of each other. With the increase of azimuthal perturbations, the thermal mode becomes more unstable and the viscous mode more stable, but there has no effect on acoustic mode. For geometrically slim and advection-dominated disks, the azimuthal perturbation and increasing of advection do not affect the stability of all the modes.