Bulge formation by the coalescence of giant clumps in primordial disk
  galaxies
  The observations and evolution of clumpy, high-redshift galaxies are
reviewed. Models suggest that the clumps form by gravitational instabilities in
a gas-rich disk, interact with each other gravitationally, and then merge in
the center where they form a bulge. The model requires smooth gas accretion
during galaxy growth.
