Topological Disorder in Spin Models on Hierarchical Lattices

A general approach for the description of spin systems on hierarchial lattices with coordination number $q$ as a dynamical variable is proposed. The ferromagnetic Ising model on the Bethe lattice was studied as a simple example demonstrating our method. The annealed and partly annealed versions of disorder concerned with the lattice coordination number are invented and discussed. Recurrent relations are obtained for the evaluation of magnetization. The magnetization is calculated for the particular disorder choices, $q=2,3$ and $q=3,4$. A nontrivial localization of critical point is revealed.