Description:

Abstract: 

Standard accretion disk theory does a pretty good job of explaining the overall energetics of gas draining into black holes, but it fails in most other respects.  It underpredicts disk thicknesses, inflow speeds and temperatures; predicts violent instabilities that are not seen; and implies that matter feeding the monster black holes in quasars should instead fragment and form stars, leaving the black hole nearly dormant.  The problem seems to be that the theory underestimates the effects of organized magnetic fields on disk structure.  I will discuss how a relatively weak magnetic field, threading the disk, can get amplified so much that it puffs the disk up, utterly changing its structure and potentially resolving the problems mentioned above.    

Speaker: Mitch Begelman, Professor, University of Colorado, Boulder

Host: Professor Giacomo Fragione