The renormalization group improved effective potential in massless models

The effective potential $V$ is considered in massless $\lambda\phi^4_4$ theory. The two conditions that the renormalization group equation be satisfied and that $V^\prime(v) =0$ (where $v$ is the vacuum expectation value of the scalar $\phi$) are sufficient to determine $V$ provided $v\neq 0$. The dependence of $V$ on $\phi$ then drops out