  Collective motion is a manifestation of emergent phenomena in medium-heavy
and heavy nuclei. A relatively large number of constituent nucleons contribute
coherently to nuclear excitations (vibrations, rotations) that are
characterized by large electromagnetic moments and transition rates. Basic
features of collective excitations are reviewed, and a simple model introduced
that describes large-amplitude quadrupole and octupole shape dynamics, as well
as the dynamics of induced fission. Modern implementations of the collective
Hamiltonian model are based on the microscopic framework of energy density
functionals, that provide an accurate global description of nuclear ground
states and collective excitations. Results of illustrative calculations are
discussed in comparison with available data.
