Some Critical Properties of the Eight-Vertex Model

The eight-vertex model solved by Baxter is shown to be equivalent to two Ising models with nearest-neighbor coupling interacting with one another via a four-spin coupling term. The critical properties of the model in the weak-coupling limit are in agreement with the scaling hypothesis. In this limit where α→0, the critical indices obey γγ₀=ββ₀=νν₀=1-1/2α, δδ₀=ηη₀=1, with the subscripts zero denoting the index values for the ordinary two-dimensional Ising model.