ARTST 102


Noboru Matsuo



The Ising Model

The Ising Model was originally developed to explain the physical alignment of particles within a magnetically-charged material, such as iron. Today, the field of statistical physics applies the Ising model to a diverse range of applications, such as social networks, flocking algorithims and the complex networks of computers connected to the Internet.

This Ising model was proposed in the 1924 doctoral thesis of Ernst Ising, a student of W. Lenz. Ising tried to explain certain empirically observed facts about ferromagnetic materials using a model of proposed by Lenz (1920). It was referred to in Heisenberg's (1928) paper which used the exchange mechanism to describe ferromagnetism. The name became well-established with the publication of a paper by Peierls (1936), which gave a non-rigorous proof that spontaneous magnetization must exist. A breakthrough occurred when it was shown that a matrix formulation of the model allows the partition function to be related to the largest eigenvalue of the matrix (Kramers and Wannier 1941, Montroll 1941, 1942, Kubo 1943). Kramers and Wannier (1941) calculated the Curie temperature using a two-dimensional Ising model, and a complete analytic solution was subsequently given by Onsager (1944). (Wolfram).

The Ising model tries to imitate behaviour in which individual elements (e.g., atoms, animals, protein folds, biological membrane, social behavior, etc.) modify their behavior so as to conform to the behavior of other individuals in their vicinity. The Ising model has more recently been used to model phase separation in binary alloys and spin glasses. In biology, it can model neural networks, flocking birds, or beating heart cells. It can also be applied in sociology. More than 12,000 papers have been published between 1969 and 1997 using the Ising model (Wolfram).

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