Effective Theory For Quantum Spin System In Low Dimension - Beyond Long-Wavelength Limit

An effective theory for quantum spin system in low dimension is constructed in the finite-q regime. It is shown that there are field configurations for which Wess-Zumino term contributes to the partition functions as topological term for ferromagnet as well as antiferromagnet in both one and two dimensional lattice,in contrast to the long wave length regime.