Journal of Statistical Physics, Vol. 56, Nos. 1/2, 1989. p. 33-42.
The inverse two-spin correlation function of a one-dimensional three-state Ports lattice with constant nearest-neighbor interactions in a uniform external field is derived exactly, It is shown that the external field induces long-range correlations. The inverse two-spin correlation function decays in a monotonic exponential fashion for a ferromagnetic lattice, while it decays in an oscillatory exponential fashion for an antiferromagnetic lattice. With no external field the inverse two-spin correlation function has a finite range equal to that of the interactions.