Time-dependent correlations for axially symmetric infinite-range spin Hamiltonians

Abstract
The time-correlation functions 〈s^x(t)s^x(0)〉 and 〈s^x(t)s^y(0)〉 are evaluated for an arbitrary infinite-range axially symmetric Hamiltonian with an arbitrary elementary spin. The behavior above the critical temperature as well as that for the three possible types of ordered phases (XY-like, intermediate, and Ising-like) is presented. Some physical consequences are discussed.