2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189791Two approaches to renormalization-group improvement are examined: the substitution of the solutions of running couplings, masses and fields into perturbatively computed quantities is compared with the systematic sum of all the leading log (LL), next-to-leading log (NLL) etc. contributions to radiatively corrected processes, with n-loop expressions for the running quantities being responsible for summing N^{n}LL contributions. A detailed comparison of these procedures is made in the context of the effective potential V in the 4-dimensional O(4) massless $λϕ^{4}$ model, showing the distinction between these procedures at two-loop order when considering the NLL contributions to the effective potential V.6 pagesHigh Energy Physics - Theorytext