Consistency in perturbative calculations and radiatively induced Lorentz and CPT violations

The origin of the radiatively induced Lorentz and CPT violations, in perturbative evaluations, of an extended version of QED, is investigated. Using a very general calculational method, concerning the manipulations and calculations involving divergent amplitudes, we clearly identify the possible sources of contributions for the violating terms. We show that consistency in the perturbative calculations, in a broader sense, leaves no room for the existence of radiatively induced contributions, which is in accordance with what was previously conjectured and recently advocated by some authors supported on general arguments.