arXiv subjects

A. F. Ferrari

Publications and source records attributed to A. F. Ferrari.

At least 19 recordsLinked to original sources

arXiv2024

Field sources in a planar anisotropic CPT-odd gauge model

In the present paper we study some new classical Lorentz violating effects in planar electrodynamics due to the presence of stationary point-like field sources. Starting from the Carroll-Field-Jackiw model defined in (3+1) dimensions, which belongs to the electromagnetic CPT-odd sector of the Standard Model Extension (SME), we apply the dimensional reduction procedure obtaining a (2+1)-dimensional model that encompasses an electromagnetic sector composed of the Maxwell-Chern-Simons electrodynamics, a pure scalar sector described by a massless Klein-Gordon field, and a mixed sector where the background vector mediates contributions involving both the scalar and the gauge fields. For all the sectors of this planar theory, we explore some physical phenomena that arise from the interactions between external sources. Specifically, we obtain perturbative effects up to second order in the background vector related to the presence of both electric and scalar planar charges and Dirac points.

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arXiv2023

Axion-Photon Interaction from Nonminimal Dimension-5 Lorentz-Violating Operators

In this paper, we discuss various possible schemes for the perturbative generation of the axion-photon interaction term in different Lorentz-breaking extensions of QED, involving operators with mass dimensions up to 5. We demonstrate explicitly that there are only a few schemes allowing to generate a finite axion-photon interaction term from one-loop radiative corrections, and within all these schemes, the generated term turns out to be ambiguous.

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arXiv2023

Lorentz Violating Electrodynamics with sources and mirrors

We look for modifications that can be derived from the Maxwell sector of the SME for the interaction between electrical charges and the electromagnetic field. The kind of problem that we are looking into is the one that might be found in a standard textbook on electromagnetism: given a set of electrical charges, in the presence of some non-trivial boundary condition (such as a mirror), find the electromagnetic field and the interaction energy between those charges. To study such kind of problem in the presence of LV coefficients, we calculate the modified propagator for the Maxwell field, and use it to calculate energy of a system given by an semi-transparent mirror and a point-like charge. We show how new effects appear in this case, such as a spontaneous torque acting on the system.

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arXiv2023

One-loop calculations in Lorentz-breaking theories and proper-time method

We discuss applications of the proper-time method in various minimal Lorentz violating modifications of QED and present new results obtained with its use. Explicitly. we calculate the complete one-loop Heisenberg-Euler effective action involving all orders in $F_{mn}$, for two of the most studied minimal Lorentz-violating extensions of QED, the one characterized by the axial vector $b^m$ and the one involving the second-rank constant tensor $c^{mn}$.

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arXiv2023

Perturbative generation of photon Lorentz violating terms from a pseudo-tensor Lorentz-breaking extension of QED

We consider an extended QED with the addition of a dimension-five Lorentz-breaking coupling between spinor and gauge fields, involving a pseudo-tensor $κ^{μνλρ}$. The specific form of the Lorentz violating coupling considered by us have been suggested in other works, and some of its consequences at the classical level were already studied. Here, we investigate the consequences of this specific form of Lorentz violation at the quantum level, evaluating the one loop corrections to the gauge field two-point function, both at zero and at finite temperature. We relate the terms that are generated by quantum corrections with the photon sector of the Standard Model Extension, discussing the possibility of establishing experimental bounds on $k^{μνρσ}$. From the dispersion relations in the resulting theory, we discuss its consistency from the causality viewpoint.

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arXiv2022

Renormalization group improvement of the effective potential in a (1+1) dimensional Gross-Neveu model

In this work, we investigate the consequences of the Renormalization Group Equation (RGE) in the determination of the effective potential and the study of Dynamical Symmetry Breaking (DSB) in an Gross-Neveu (GN) model with N fermions fields in (1+1) dimensional space-time, which can be applied as a model to describe certain properties of the polyacetylene. The classical Lagrangian of the model is scale invariant, but radiative corrections to the effective potential can lead to dimensional transmutation, when a dimensionless parameter (coupling constant) of the classical Lagrangian is exchanged for a dimensionful one, a dynamically generated mass for the fermion fields. For the model we are considering, perturbative calculations of the effective potential and renormalization group functions up to three loops are available, but we use the RGE and the leading logs approximation to calculate an improved effective potential, including contributions up to six loops orders. We then perform a systematic study of the general aspects of DSB in the GN model with finite N, comparing the results we obtain with the ones derived from the original unimproved effective potential we started with.

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arXiv2022

Semi-transparent boundaries in CPT-even Lorentz violating electrodynamics

Some aspects of the nonbirefringent CPT-even gauge sector of the Standard Model Extension (SME), in the vicinity of a semi-transparent mirror, are investigated in this paper. We first consider a model where the Lorentz symmetry breaking is caused by a single background vector $v^μ$, and we obtain perturbative results up to second order in $v^μ$. Specifically, we compute the modified propagator for the gauge field due to the presence of the mirror and we analyze the corresponding interaction between the mirror and a stationary point-like charge. We show that when the charge is placed in the vicinity of the mirror, a spontaneous torque emerges, which is a new effect with no counterpart in Maxwell electrodynamics. We also compare these results with the corresponding ones obtained for the Lorentz violating scalar field theory. As expected, in the limiting case of perfect mirrors, we recover the interaction found via the image method. Finally, we discuss how we can extend these results for a more general Lorentz violating background.

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arXiv2022

External sources in a minimal and nonminimal CPT-odd Lorentz violating Maxwell electrodynamics

This paper is devoted to the study of interactions between stationary electromagnetic sources for the minimal and nonminimal CPT-odd photon sector of the Standard Model Extension (SME), where we search mainly for physical phenomena not present in the Maxwell electrodynamics. First we consider the minimal CPT-odd sector, where the Lorentz violation is caused by the Carroll-Field-Jackiw (CFJ) term, namely $\simε^{μναβ}\left(k_{AF}\right)_μA_νF_{αβ}$, and we treat the Lorentz breaking parameter $\left(k_{AF}\right)^μ$ perturbatively up to second order. We consider effects due to the presence of point-like charges, Dirac strings and point-like dipoles. In special, we calculate the electromagnetic field produced outside the string and investigate the so called Aharonov-Bohm bound states in Lorentz violation context. After, we consider a model where the Lorentz violation is generated by the higher-derivative version of the CFJ model, namely $\simε^{μναβ}V_μA_ν\Box F_{αβ}$, which is a dimension five term of the CPT-odd sector of the nonminimal SME. For this higher-derivative model, we obtain effects up to second order in $V^μ$ related to the presence of point-like charges and a steady current line. We use overestimated constrains for the Lorentz violation parameters in order to investigate the physical relevance of some results found in atomic systems. We also make an overestimate for the background vectors using experimental data from the atomic electric field.

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arXiv2021

Effective potential and dynamical symmetry breaking up to five loops in a massless abelian Higgs model

In this paper, we investigate the application of the Renormalization Group Equation (RGE) in the determination of the effective potential and the study of Dynamical Symmetry Breaking (DSB) in a massless Abelian Higgs (AH) model with an N-component complex scalar field in (3+1) dimensional spacetime. The classical Lagrangian of this model has scale invariance, which can be broken by radiative corrections to the effective potential. It is possible to calculate the effective potential using the RGE and the renormalization group functions that are obtained directly from loop calculations of the model and, using the leading logs approximation, information about higher loop orders can be included in the effective potential thus obtained. To show this, we use the renormalization group functions reported in the literature, obtained with a four loop calculation, and obtain a five loop approximation to the effective potential, in doing so, we have to properly take into account the fact that the model has multiple scales, and convert the functions that were originally calculated in the minimal subtraction (MS) renormalization scheme to another scheme which is adequate for the RGE method. This result is then used to study the DSB, and we present evidence for a rich structure of classical vacua, depending on the value of gauge coupling constant and number of scalar fields, which are considered as free parameters.

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arXiv2020

Mirrors and field sources in a Lorentz-violating scalar field theory

In this paper we consider different classical effects in a model for a scalar field incorporating Lorentz symmetry breaking due to the presence of a single background vector v^μ coupled to its derivative. We perform an investigation of the interaction energy between stationary steady sources concentrated along parallel branes with an arbitrary number of dimensions, and derive from this study some physical consequences. For the case of the scalar dipole we show the emergence of a nontrivial torque, which is distinctive sign of the Lorentz violation. We also investigate a similar model in the presence of a semi-transparent mirror. For a general relative orientation between the mirror and the v^μ, we are able to perform calculations perturbatively in v^μ up to second order. We also find results without recourse to approximations for two special cases, that of the mirror and v^μ being parallel or perpendicular to each other. For all these configurations, the propagator for the scalar field and the interaction force between the mirror and a point-like field source are computed. It is shown that the image method is valid in our model for the Dirichlet's boundary condition, and we argue that this is a non-trivial result. We also show the emergence of a torque on the mirror depending on its orientation with respect to the Lorentz violating background. This is a new effect with no counterpart in theories with Lorentz symmetry in the presence of mirrors.

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arXiv2019

The point-charge self-energy in a nonminimal Lorentz violating Maxwell Electrodynamics

In this letter we study the self-energy of a point-like charge for the electromagnetic field in a non minimal Lorentz symmetry breaking scenario in a $n+1$ dimensional space time. We consider two variations of a model where the Lorentz violation is caused by a background vector $d^ν$ that appears in a higher derivative interaction. We restrict our attention to the case where $d^μ$ is a time-like background vector, namely $d^{2}=d^μd_μ>0$, and we verify that the classical self-energy is finite for any odd spatial dimension $n$ and diverges for even $n$. We also make some comments regarding obstacles in the quantization of the proposed model.

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arXiv2019

Lorentz Violation and Radiative Corrections in Gauge Theories

Various studies have already considered radiative corrections in Lorentz-violating models unveiling many instances where a minimal or nonminimal operator generates, via loop corrections, a contribution to the photon sector of the Standard-Model Extension. However, an important fraction of this literature does not follow the widely accepted conventions and notations of the Standard-Model Extension, and this obscures the comparison between different calculations as well as possible phenomenological consequences. After reviewing some of these works, we uncover one example where a well defined loop correction to the $k_{F}$ coefficient, already presented in the literature, allows us to improve the bounds on one specific coefficient of the fermion sector of the Lorentz-violating QED extension.

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arXiv2018

Radiative corrections and Lorentz violation

Radiative corrections in Lorentz violating (LV) models have already received a lot of attention in the literature in recent years, with many instances where a LV operator in one sector of the Standard Model Extension (SME) generates, via loop corrections, one of the LV coefficients in the photon sector, which is probably the most understood and well constrained part of the SME. In many of these works, however, the now standard notation of the SME is not used, which can obscure the comparison of different results, and their possible phenomenological relevance. In this work, we fill this gap, trying to build up a more general perspective on the topic, bringing many of the results to the SME conventional notation and commenting on their possible phenomenological relevance. We uncover one example where a result already presented in the literature can be used to place a stronger bound on the temporal component of the b_μ coefficient of the fermion sector of the SME.

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arXiv2018

Reduction of order and Fadeev-Jackiw formalism in generalized electrodynamics

The aim of this work is to discuss some aspects of the reduction of order formalism in the context of the Fadeev-Jackiw symplectic formalism, both at the classical and the quantum level. We start by reviewing the symplectic analysis in a regular theory (a higher derivative massless scalar theory), both using the Ostrogradsky prescription and also by reducing the order of the Lagrangian with an auxiliary field, showing the equivalence of these two approaches. The interpretation of the degrees of freedom is discussed in some detail. Finally, we perform the similar analysis in a singular higher derivative gauge theory (the Podolsky electrodynamics), in the reduced order formalism: we claim that this approach have the advantage of clearly separating the symplectic structure of the model into a Maxwell and a Proca (ghost) sector, thus complementing the understanding of the degrees of freedom of the theory and simplifying calculations involving matrices.

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arXiv2018

$CP^{(N-1)}$ model in aether-superspace

In this paper we study the dynamical generation of mass in the Lorentz-violating $CP^{(N-1)}$ model defined in two and three-dimensional aether-superspace. We show that even though the model presents a phase structure similar to the usual, Lorentz invariant case, the dynamically generated mass by quantum corrections has a dependence on the Lorentz violating background properties, except for spacelike LV vector parameter. This is to be contrasted with the behavior of the quantum electrodynamics in the two-dimensional aether-superspace, where the dynamical generation of mass was shown to exhibit an explicit dependence on the aether parameters in every possible case.

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arXiv2017

The role of singular spinor fields in a torsional gravity, Lorentz-violating, framework

In this work, we consider a generalization of quantum electrodynamics including Lorentz violation and torsional-gravity, in the context of general spinor fields as classified in the Lounesto scheme. Singular spinor fields will be shown to be less sensitive to the Lorentz violation, as far as couplings between the spinor bilinear covariants and torsion are regarded. In addition, we prove that flagpole spinor fields do not admit minimal coupling to the torsion. In general, mass dimension four couplings are deeply affected when singular flagpole spinors are considered, instead of the usual Dirac spinors. We also construct a mapping between spinors in the covariant framework and spinors in Lorentz symmetry breaking scenarios, showing how one may transliterate spinors of different classes between the two cases. Specific examples concerning the mapping of Dirac spinor fields in Lorentz violating scenarios into flagpole and flag-dipole spinors with full Lorentz invariance (including the cases of Weyl and Majorana spinors) are worked out.

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arXiv2016

New effects in the interaction between electromagnetic sources mediated by nonminimal Lorentz violating interactions

This paper is dedicated to the study of interactions between external sources for the electromagnetic field in a Lorentz symmetry breaking scenario. We focus on a particular higher derivative, Lorentz violating interaction that arises from a specific model that was argued to lead to interesting effects in the low energy phenomenology of light pseudoscalars interacting with photons. The kind of higher derivative Lorentz violating interaction we discuss do not appear in the well known Standard Model Extension, therefore they are called nonminimal. They are usually expected to be relevant only at very high energies, but we argue they might also induce relevant effects in low energy phenomena. Special attention is given for phenomena that have no counterpart in Maxwell theory.

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arXiv2016

Twisted Supersymmetry in a Deformed Wess-Zumino Model in (2+1) Dimensions

Non-anticommutative deformations have been studied in the context of supersymmetry (SUSY) in three and four space-time dimensions, and the general picture is that highly nontrivial to deform supersymmetry in a way that still preserves some of its important properties, both at the formal algebraic level (e.g., preserving the associativity of the deformed theory) as well as at the physical level (e.g., maintaining renormalizability). The Hopf algebra formalism allows the definition of algebraically consistent deformations of SUSY, but this algebraic consistency does not guarantee that physical models build upon these structures will be consistent from the physical point of view. We will investigate a deformation induced by a Drinfel'd twist of the ${\cal N}=1$ SUSY algebra in three space-time dimensions. The use of the Hopf algebra formalism allows the construction of deformed ${\cal N}=1$ SUSY algebras that should still preserve a deformed version of supersymmetry. We will construct the simplest deformed version of the Wess-Zumino model in this context, but we will show that despite the consistent algebraic structure, the model in question is not invariant under SUSY transformation and is not renormalizable. We will comment on the relation of these results with previous ones discussed in the literature regarding similar four-dimensional constructions.

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