Quartic interaction

In quantum field theory, a quartic interaction is a type of self-interaction in a scalar field. Other types of quartic interactions may be found under the topic of four-fermion interactions. A classical free scalar field ${\displaystyle \varphi }$ satisfies the Klein–Gordon equation. If a scalar field is denoted ${\displaystyle \varphi }$, a quartic interaction is represented by adding a potential energy term ${\displaystyle ({\lambda }/{4!})\varphi ^{4}}$ to the Lagrangian density. The coupling constant ${\displaystyle \lambda }$ is dimensionless in 4-dimensional spacetime.

This article uses the ${\displaystyle (+---)}$ metric signature for Minkowski space.