On phase separation points for one-dimensional models

In the paper, the one-dimensional model with nearest-neighbor interactions I _n , n ∈ Z, and the spin values ±1 is considered. It is known that, under some conditions on parameters of I _n , a phase transition occurs for this model. We define the notion of a phase separation point between two phases. We prove that the expectation value of this point is zero and its mean-square fluctuation is bounded by a constant C(β) which tends to ¼ as β → ∞, where β = 1/T and T is the temperature.