natural correspondence between the left-handed and the right-handed flavors), U(1)Q is the Dirac charge, which is sometimes called the baryon number and U(1)χ is the axial charge. If a chiral condensate forms, then the chiral symmetry is spontaneously broken into a diagonal subgroup SU(N) since the condensate leads to a pairing of the left-handed and the right-handed flavors. The axial charge is also spontaneously broken. The broken symmetries lead to massless pseudoscalar bosons which are sometimes called pions. See Goldstone boson. As mentioned, this model is sometimes used as a phenomenological model of quantum chromodynamics in the chiral limit. However, while it is able to model chiral symmetry breaking and chiral condensates, it does not model confinement. Also, the axial symmetry is broken spontaneously in this model, leading to a massless Goldstone boson unlike QCD, where it is broken anomalously. Since the Nambu–Jona-Lasinio model is nonrenormalizable in four spacetime dimensions, this theory can only be an effective field theory which needs to be UV completed. See also Gross–Neveu model References External links Giovanni Jona-Lasinio and Yoichiro Nambu, Nambu-Jona-Lasinio model, Scholarpedia, 5(12):7487, (2010). doi:10.4249/scholarpedia.7487 Quantum chromodynamics Superconductivity