Thirring model

The Thirring model is an exactly solvable quantum field theory which describes the self-interactions of a Dirac field in (1+1) dimensions.

The Thirring model is given by the Lagrangian density

where ${\displaystyle \psi =(\psi _{+},\psi _{-})}$ is the field, g is the coupling constant, m is the mass, and ${\displaystyle \gamma ^{\mu }}$, for ${\displaystyle \mu =0,1}$, are the two-dimensional gamma matrices.

...
Wikipedia