  There is increasing evidence for the presence of blue super star clusters in
the central regions of ultraluminous infrared galaxies like Arp 220.
Ultraluminous galaxies are thought to be triggered by galaxy mergers, and it
has often been argued that these super star clusters may form during violent
collisions between gas clouds in the final phase of the mergers. We now
investigate another set of models which differ from previous ones in that the
formation of the super star clusters is linked directly to the very intense
starburst occurring at the very center of the galaxy. Firstly we show that a
scenario in which the super star clusters form in material compressed by shock
waves originating from the central starburst is implausible because the objects
so produced are much smaller than the observed star clusters in Arp 220. We
then investigate a scenario (based on the Shlosman-Noguchi model) in which the
infalling dense gas disk is unstable gravitationally and collapses to form
massive gaseous clumps. Since these clumps are exposed to the external high
pressure driven by the superwind (a blast wave driven by a collective effect of
a large number of supernovae in the very core of the galaxy), they can collapse
and then massive star formation may be induced in them. The objects produced in
this kind of collapse have properties consistent with those of the observed
super star clusters in the center of Arp 220.
