The model is much inspired by the different field of solid state theory, particularly from the BCS breakthrough of 1957.
[1] A subsequent paper included chiral symmetry breaking, isospin and strangeness.
[2] Around that time, the same model was independently considered by Soviet physicists Valentin Vaks and Anatoly Larkin.
It is an example of the importance of four-fermion interactions and is defined in a spacetime with an even number of dimensions.
It is still important and is used primarily as an effective although not rigorous low energy substitute for quantum chromodynamics.
Starting with the one-flavor case first, the Lagrangian density is or, equivalently, decomposed into left and right chiral parts, The terms proportional to
The broken symmetries lead to (nearly) massless pseudoscalar bosons, e.g. pions.