Partition function of a finite Ising model on a torus
T. Morita · Journal of Physics A Mathematical and General · 1986
The detailed proof presented in an earlier paper, justifying Vdovichenko's method (1965) which gives an exact expression of the free energy of the Ising model in a plane, is extended to the system on a torus. This justifies the exact expression of the free energy in the form given by Vdovichenko for the Ising model on the general two-dimensional lattice in the thermodynamic limit.