  The smooth topology change of Berry's phase from a Dirac monopole-like
configuration to a dipole configuration, when one approaches the monopole
position in the parameter space, is analyzed in an exactly solvable model. A
novel aspect of Berry's connection ${\cal A}_{k}$ is that the geometrical
center of the monopole-like configuration and the origin of the Dirac string
are displaced in the parameter space. Gauss' theorem $\int_{S}(\nabla\times
{\cal A})\cdot d\vec{S}=\int_{V} \nabla\cdot (\nabla\times {\cal A}) dV=0$ for
a volume $V$ which is free of singularities shows that a combination of the
monopole-like configuration and the Dirac string is effectively a dipole. The
smooth topology change from a dipole to a monopole with a quantized magnetic
charge $e_{M}=2\pi\hbar$ takes place when one regards the Dirac string as
unobservable if it satisfies the Wu-Yang gauge invariance condition. In the
transitional region from a dipole to a monopole, a half-monopole appears with
an observable Dirac string, which is analogous to the Aharonov-Bohm phase of an
electron for the magnetic flux generated by the Cooper pair condensation. The
main topological features of an exactly solvable model are shown to be
supported by a generic model of Berry's phase.
