Massive stars in sub-parsec rings around galactic centers
  We consider the structure of self-gravitating marginally stable accretion disks in galactic centers in which a small fraction of the disk mass has been converted into proto-stars. We find that proto-stars accrete gaseous disk matter at prodigious rates. Mainly due to the stellar accretion luminosity, the disk heats up and geometrically thickens, shutting off further disk fragmentation. The existing proto-stars however continue to gain mass by gas accretion. As a results, the initial mass function for disk-born stars at distances R ~ 0.03-3 parsec from the super-massive black hole should be top-heavy. The effect is most pronounced at around R ~ 0.1 parsec. We suggest that this result explains observations of rings of young massive stars in our Galaxy and in M31, and predict that more of such rings will be discovered. 
Sergei Nayakshin (U of Leicester)