  The influence of topological defects on phase synchronization and phase
coherence in two-dimensional arrays of locally-coupled, nonidentical, chaotic
oscillators is investigated. The motion of topological defects leads to a
breakdown of phase synchronization in the vicinities of the defects; however,
the system is much more phase coherent as long as the coupling between the
oscillators is strong enough to prohibit the continuous dynamical creation and
annihilation of defects. The generic occurrence of topological defects in two
and higher dimensions implies that the concept of phase synchronization has to
be modified for these systems.
