One-loop conformal anomaly in an implicit momentum space regularization framework

In this paper we consider matter fields in a gravitational background in order to compute the breaking of the conformal current at one-loop order. Standard perturbative calculations of conformal symmetry breaking expressed by the non-zero trace of the energy-momentum tensor have shown that some violating terms are regularization dependent, which may suggest the existence of spurious breaking terms in the anomaly. Therefore, we perform the calculation in a momentum space regularization framework in which regularization dependent terms are judiciously parametrized. We compare our results with those obtained in the literature and conclude that there is an unavoidable arbitrariness in the anomalous term $\Box R$.Comment: in European Physical Journal C, 201

Subtleties in the beta function calculation of N=1 supersymmetric gauge theories

We investigate some peculiarities in the calculation of the two-loop beta-function of $N=1$ supersymmetric models which are intimately related to the so-called "Anomaly Puzzle". There is an apparent paradox when the computation is performed in the framework of the covariant derivative background field method. In this formalism, it is obtained a finite two-loop effective action, although a non-null coefficient for the beta-function is achieved by means of the renormalized two-point function in the background field. We show that if the standard background field method is used, this two-point function has a divergent part which allows for the calculation of the beta-function via the renormalization constants, as usual. Therefore, we conjecture that this paradox has its origin in the covariant supergraph formalism itself, possibly being an artifact of the rescaling anomaly.Comment: Few misprintings corrected and comments added. To meet the version to be published at European Physical Journal

Dual embedding of extended models with a Lorentz-breaking mass term

In this paper, we investigate a CPT-even model with a Lorentz-violating mass term. Such kind of models may present very interesting features like superluminal modes of propagation or even instantaneous long-range interactions. The mass term we investigate can be induced at classical or quantum level in a scenario with spontaneous gauge symmetry breaking in a gauge-Higgs model without Lorentz symmetry. We analyze the physical consistency of the model by studying the poles of the propagator. By using the Noether Dualization Method (NDM), we obtain a gauge invariant dual theory for this model. The physical equivalence between the two models is investigated and a general relation between the two propagators is obtained.Comment: 16 pages. Improved version accepted by Physical Review

Ambiguities in the gravitational correction of quantum electrodynamics

We verify that quadratic divergences stemming from gravitational corrections to QED which have been conjectured to lead to asymptotic freedom near Planck scale are arbitrary (regularization dependent) and compatible with zero. Moreover we explicitly show that such arbitrary term contributes to the beta function of QED in a gauge dependent way in the gravitational sector