  The recently realized multicomponent Bose-Einstein condensates provide
opportunities to explore the rich physics brought about by the spin degrees of
freedom. For instance, we can study spin waves and phase separation,
macroscopic quantum tunneling, Rabi oscillations, the coupling between spin
gradients and superfluid flow, squeezed spin states, vortices and other
topological excitations. Theoretically, there have been already some studies of
the ground-state properties of these systems and their line-like vortex
excitations. In analogy with nuclear physics or the quantum Hall effect, we
explore here the possibility of observing point-like topological excitations or
skyrmions. These are nontrivial spin textures that in principle can exist in a
spinor Bose-Einstein condensate. In particular, we investigate the stability of
skyrmions in a fictitious spin-1/2 condensate of Rb87 atoms. We find that
skyrmions can exist in this case only as a metastable state, but with a
lifetime of the order of, or even longer than, the typical lifetime of the
condensate itself. In addition to determining the size and the lifetime of the
skyrmion, we also present its spin texture and finally briefly consider its
dynamical properties.
