### THE NAMBU--JONA-LASINIO MODEL

The Nambu--Jona-Lasinio (NJL) model is a model in which the hadron masses are
generated by spontaneous symmetry breaking of the vacuum. In the modern form of the NJL
model, we start with essentially massless quarks with zero range
interactions between them, but with a cutoff in momentum space. Thus it is a
low energy approximation to QCD in which form factor and other finite range
effects have been ignored. The NJL model is only an effective theory, and it does not lead to
quark confinement. However, it may work quite well in the region of interest in nuclear physics,
i.e. for excitations less than the scalar meson mass.
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