Resumen: A new approach to the path integral over fermionic fields, based on the extension of a reformulation of the adiabatic approximation to some quantum-mechanical systems, is presented. A novel non-analytic contribution to the effective fermionic action for a fermion field coupled to a non-Abelian vector field is identified. The possible interpretation of this contribution as a violation of the decoupling theorem in quantum field theory (QFT) is discussed. The generalization of the approach to the case of finite temperature and density suggests the possibility to apply it to the understanding of non-perturbative properties in QFT and their dependence on temperature and density. Idioma: Inglés DOI: 10.1016/j.physletb.2005.04.044 Año: 2005 Publicado en: Physics Letters B 619, 3-4 (2005), 367-376 ISSN: 0370-2693 Factor impacto JCR: 5.301 (2005) Categ. JCR: PHYSICS, MULTIDISCIPLINARY rank: 6 / 68 = 0.088 (2005) - Q1 - T1 Financiación: info:eu-repo/grantAgreement/ES/MCYT/FPA2003-02948 Tipo y forma: Artículo (Versión definitiva) Área (Departamento): Área Física Teórica (Dpto. Física Teórica)