On a Phase Separation Point for One - Dimensional Models

Abstract

In the paper a one-dimensional model with nearest - neighbor interactions $I_n, n\in \Z$ and spin values $\pm 1$ is considered. It is known that under some conditions on parameters $I_n$ the phase transition occurs for the model. We define a notion of "phase separation" point between two phases. We prove that the expectation value of the point is zero and its the mean square fluctuation is bounded by a constant $C(\beta)$ which tends to 1/4 if $\beta\to\infty$. Here $\beta=\frac{1}{T}$, $ T>0$-temperature.