The hierarchical parity model

Hierarchical spin-glasses are Ising spin models defined by recursively coupling together two equally-sized sub-systems. In this work a new hierarchical system is introduced wherein the sub-systems coupled through parity of their spins. Exact Renormalization Group recursion equations for many correlators may be derived Parity Model, even completely general couplings. Moreover, model computationally tractable in that O(N) algorithms exist computation partition function and ground state energy. special case where couplings all equal, shown to exhibit thermal phase transition.