In quantum field theory, the Thirring model is a model of a self-interacting Dirac field. In particular, if ψ is a Dirac spinor field, the Lagrangian density is given by Quantum field theory (QFT) is the application of quantum mechanics to fields. ... In physics, a Dirac field is a fermionic field (usually a quantized field, as usual in quantum field theory) associated with spin 1/2 fermions such as the electron or muon. ... A Lagrangian of a dynamical system, named after Joseph Louis Lagrange, is a functional of the dynamical variables which concisely describes the equations of motion of the system. ...

where g is the coupling constant and γ is the gamma matrix and m is the mass. In physics, a coupling constant, usually denoted g, is a number that determines the strength of an interaction. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ...

Sign conventions might vary. In some physics textbooks and articles, certain quantities are defined with the opposite sign from that which is used in other publications. ...