2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203988Explicit counterterm construction is presented in a symmetry breaking background for the 2PI effective action of the self-interacting one-component scalar field including skeleton diagrams to O(λ^2). The applied strategy is an extension of our treatment of the 2PI-Hartree approximation [G. Fejos, A. Patkos and Zs. Szep, Nucl. Phys. A803 (2008) 135]. The procedure is also applied to the O(N) model.23 pages, 2 figures, typos corrected. Version published in Nucl. Phys. AHigh Energy Physics - Phenomenologytext