# Nonlinerality of QFT

by gentsagree
Tags: nonlinerality
 P: 47 Nonlinearlity of QFT produces interactions, or so I was told today. Maxwell's eqns, though, are perfectly linear. Does that mean that Maxwell's eqns don't predict interactions? Thanks
 P: 1,020 Free field theories in which no interaction is present(of course) are linear,you add a nonlinear term to account for interaction like in $\phi^4$ theory in which a self interacting term is present.But that does not mean that interaction term is always nonlinear but nature does not chose one.Maxwell's eqns are linear but they still have interaction.
 Mentor P: 11,925 The Maxwell equations don't lead to self-interaction. That is perfectly fine, as there is no direct (without other fields involved) self-interaction of electromagnetic fields. In addition, "Nonlinearlity of QFT produces interactions" does not mean the reverse ("Interactions in QFT have to come from nonlinearity") has to be true.