Solution
= Solution
No. With only $\lambda_0\phi^6$, the free energy has an exact <Z2 symmetry> $\phi\mapsto-\phi$. Integrating out fast modes and rescaling preserve that symmetry, whereas $\phi^5$ is odd. Therefore no five-point vertex and no correction to $\gamma(\zeta)$ can be generated at any order in $\lambda_0$.