One-Dimensional Chain of Anisotropic Spin-Spin Interactions. II. Properties of the Ground-State Energy Per Lattice Site for an Infinite System

Abstract

The ground-state energy $2f$ per lattice site for an infinite system is studied as a function of $\Delta$ and of the magnetization $y$. Analyticity properties of $f(\Delta , y)$ are proved. The behavior of $f(\Delta , y)$ at and near $y=0\mathrm{}$ and $y=1\mathrm{}$ are investigated.