The isotropic model on the inhomogeneous periodic chain

The static and dynamic properties of the isotropic XY-model $(s=1/2)$ on the inhomogeneous periodic chain, composed of \emph{N} segments with \emph{n} different exchange interactions and magnetic moments, in a transverse field \emph{h} are obtained exactly at arbitrary temperatures. The properties are determined by introducing the generalized Jordan-Wigner transformation and by reducing the problem to a diagonalization of a finite matrix of \emph{n-th} order. The diagonalization procedure is discussed in detail and the critical behaviour induced by the transverse field, at T=0, is presented. The quantum transitions are determined by analyzing the behaviour of the induced magnetization, defined as $(1/n)\sum_m=1ⁿμ_m$ where $μ_m$ is the magnetic moment at site \emph{m} within the segment \emph{j}, as a function of the field, and the critical fields determined exactly. The dynamic correlations, $$, and the dynamic susceptibility $χ_q^zz(ω)$ are also obtained at arbitrary temperatures. Explicit results are also presented in the limit T=0, where the critical behaviour occurs, for the static susceptibility $χ_q^zz(0)$ as a function of the transverse field \emph{h}, and for the frequency dependency of dynamic susceptibility $χ_q^zz(ω)$. Also in this limit, the transverse time-correlation $$, the dynamic and isothermal susceptibilities, $χ_q^xx(ω)$ and $χ_T^xx$, are obtained for the transverse field greater or equal than the saturation field.