  We show in this paper an interesting relation between elementary and
topological excitations in the antiferromagnetic and d-wave superconducting
phases of the t-J model at two dimenions. The topological spin and charge
excitations in one phase have the same dynamics as elementary excitations in
the other phase, except the appearance of energy gaps. Moreover, the transition
from one phase to another can be described as a quantum disordering transition
associated with the topological excitations. Based on the above picture, a
plausible phase diagram of t-J model is constructed.
