Proper noun
the Ising model
A particular mathematical model of ferromagnetism in statistical mechanics.
For example, mean field theory predicts a finite discontinuity of the heat capacity at the transition temperature, and the two-dimensional Ising model has a logarithmic divergence. Source: Internet
Later, there developed the idea that a finite number of generating operators could represent all the correlation functions of the Ising model. Source: Internet
The Ising model was solved exactly to show that spontaneous magnetization cannot occur in one dimension but is possible in higher-dimensional lattices. Source: Internet