Renormalizability of Φ-derivable approximations in scalar ϕ4 theory

We discuss the renormalizability of Φ-derivable approximations in scalar ϕ4 theory in four dimensions. The formalism leads to self-consistent equations for the 2-point and the 4-point functions which are plagued by ultraviolet divergences. Through a detailed analysis of the one and two-loop self-energy skeletons, we show that both equations can be renormalized simultaneously and determine the corresponding counterterms. These insure the elimination of ultraviolet divergences both at zero and finite temperature.