ANTIFERROMAGNETS IN 2+EPSILON DIMENSIONS

Using a perturbative approach with a modified wick theorem for a spin 1/2 antiferromagnet we find the excitation spectra, an effective exchange interaction and the staggered magnetization for the square lattice at T = O. In the framework of the non- linear sigma model we discuss the dimension shift, the influence of anisotropic and helical terms. Anisotropy leads always to a reduction of the quantum disordered fixed point. The results of large n expansion complete the conclusions of a renormalization group approach.