The S=1 quantum antiferromagnetic chain with the Hamiltonian H=
Ji SixSi+1x+
SiySi+1y+\ensuremath{\lambda}
Siz Si+1z+D(
Siz)2 is studied. By developing a (path-integral-type) stochastic geometric representation and using the ideas of percolation, we find that the Haldane phase with a unique disordered ground state and a gap can be regarded as ``liquid''. The large-D phase and the N\'eel ordered phase are identified as ``gas'' and ``solid'', respectively. We introduce a new order parameter that distinguishes the Haldane phase from other disordered phases such as the large-D phase or the dimer phase.
We study the dynamical spin excitations of the one-dimensional
S=1 Heisenberg antiferromagnetic chain with single-ion anisotropy by using quantum Monte Carlo simulations and stochastic analytic continuation of imaginary-time correlation function. Using the transverse dynamic spin structure factor, we observe the quantum phase transition with a critical point between the topological Haldane gapped phase and the trivial phase. At the quantum critical point, we find a broad continuum characterized by the Tomonaga-Luttinger liquid, and its dynamical signatures are similar to a
S=1/2 Heisenberg antiferromagnetic chain. The broad continuum can be seen as a dynamical signature of spinons. We further identify that the elementary excitations are fractionalized spinons in the critical state.