Quartic interaction generated by a sextic interaction
= Quartic interaction generated by a sextic interaction
Splitting a <scalar field> into slow and fast components $\phi=\varphi+\eta$, the <Wick contractions> in $\lambda\langle(\varphi+\eta)^6\rangle$ generate $15\lambda\langle\eta^2\rangle\varphi^4$. A vanishing bare quartic coupling is therefore not generally preserved by <renormalization-group flow>.