  A number of theoretical and simulation results on star and structure
formation in galaxy interactions and mergers is reviewed, and recent
hydrodynamic simulations are presented. The role of gravity torques and ISM
turbulence in galaxy interactions, in addition to the tidal field, is
highlighted. Interactions can drive gas inflows towards the central kpc and
trigger a central starburst, the intensity and statistical properties of which
are discussed. A kinematically decoupled core and a supermassive central black
hole can be fueled. Outside of the central kpc, many structures can form inside
tidal tails, collisional ring, bridges, including super star clusters and tidal
dwarf galaxies. The formation of super star clusters in galaxy mergers can now
be directly resolved in hydrodynamic simulations. Their formation mechanisms
and long-term evolution are reviewed, and the connection with present-day
early-type galaxies is discussed.
