Resumen: Renormalization of massless Feynman amplitudes in x-space is reexamined here, using almost exclusively real-variable methods. We compute a wealth of concrete examples by means of recursive extension of distributions. This allows us to show perturbative expansions for the four-point and two-point functions at several loop order. To deal with internal vertices, we expound and expand on convolution theory for log-homogeneous distributions. The approach has much in common with differential renormalization as given by Freedman, Johnson and Latorre; but differs in important details. Idioma: Inglés DOI: 10.1016/j.nuclphysb.2014.07.018 Año: 2014 Publicado en: NUCLEAR PHYSICS B 886 (2014), 824-869 ISSN: 0550-3213 Factor impacto JCR: 3.929 (2014) Categ. JCR: PHYSICS, PARTICLES & FIELDS rank: 7 / 27 = 0.259 (2014) - Q2 - T1 Financiación: info:eu-repo/grantAgreement/ES/MINECO/FPA2012-35453 Tipo y forma: Artículo (Versión definitiva) Área (Departamento): Física Teórica (Departamento de Física Teórica)