Running summarizing tools on a new article

Abstract: Accretion disks in active galactic nuclei (AGNs) play a central role in the complex engine operating around the central supermassive black hole. Black holes, which are at the center of all AGNs, are purely general-relativistic objects, and the description of the properties and behavior of matter and light in their vicinity requires the use of the formalism of Einstein's theory of gravitation. Very early in the studies of accretion disk physics, it became clear that, if their driving mechanism is viscous, an “anomalous”, turbulent viscosity must be at work because astrophysical disks are too large for the molecular viscosity to be efficient. The 2D structure of geometrically thin, non-self-gravitating, axially symmetric accretion disks can be split into a 1D+1D structure corresponding to a hydrostatic vertical configuration and radial quasi-Keplerian viscous flow. The chapter presents and discusses the disk thermal and the viscous instabilities.