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José A. Helayël-Neto

Publications and source records attributed to José A. Helayël-Neto.

34 records · Page 2Linked to original sources

Coulomb's law modification driven by a logarithmic electrodynamics

We examine physical aspects for the electric version of a recently proposed logarithmic electrodynamics, for which the electric field of a point-like charge is finite at the origin. It is shown that this electrodynamics displays the vacuum birefringence phenomenon in the presence of external magnetic field. Afterwards we compute the lowest-order modification to the interaction energy by means of the gauge-invariant but path-dependent variables formalism. These are shown to result in a long-range ($1/r^3$-type) correction, in addition to a linear and another logarithmic correction, to the Coulomb potential.

physics.class-ph↗

Remarks on the static potential in theories with Lorentz violation terms

We study the impact of Lorentz violating terms on a physical observable for both electrodynamics of chiral matter and an Abelian Higgs-like model in $3+1$ dimensions. Our calculation is done within the framework of the gauge-invariant, but path-dependent, variables formalism. Interestingly enough, for electrodynamics of chiral matter we obtain a logarithmic correction to the usual static Coulomb potential. Whereas for a Abelian Higgs model with a Lorentz-breaking term, our result displays new corrections to the Yukawa potential.

hep-th↗

Photon sector analysis of Super and Lorentz symmetry breaking: effective photon mass, bi-refringence and dissipation

Within the Standard Model Extension (SME), we expand our previous findings on four classes of violations of Super-Symmetry (SuSy) and Lorentz Symmetry (LoSy), differing in the handedness of the Charge conjugation-Parity-Time reversal (CPT) symmetry and in whether considering the impact of photinos on photon propagation. The violations, occurring at the early universe high energies, show visible traces at present in the Dispersion Relations (DRs). For the CPT-odd classes ($V_μ$ breaking vector) associated with the Carroll-Field-Jackiw (CFJ) model, the DRs and the Lagrangian show for the photon an effective mass, gauge invariant, proportional to $|{\vec V}|$. The group velocity exhibits a classic dependency on the inverse of the frequency squared. For the CPT-even classes ($k_{F}$ breaking tensor), when the photino is considered, the DRs display also a massive behaviour inversely proportional to a coefficient in the Lagrangian and to a term linearly dependent on $k_{F}$. All DRs display an angular dependence and lack LoSy invariance. In describing our results, we also point out the following properties: i) the appearance of complex or simply imaginary frequencies and super-luminal speeds and ii) the emergence of bi-refringence. Finally, we point out the circumstances for which SuSy and LoSy breakings, possibly in presence of an external field, lead to the non-conservation of the photon energy-momentum tensor. We do so for both CPT sectors.

hep-th↗

A note on nonlinear electrodynamics

We explore the physical consequences of a new nonlinear electrodynamics, for which the electric field of a point-like charge is finite at the origin, as in the well-known Born-Infeld electrodynamics. However, contrary to the latter, in this new electrodynamics the phenomenon of birefringence and dichroism take place in the presence of external magnetic fields. Subsequently we study the interaction energy, within the framework of the gauge-invariant but path-dependent variables formalism. Interestingly enough, the static potential profile contains a linear potential leading to the confinement of static charges.

physics.gen-ph↗

Remarks on a $B \wedge F$ model with topological mass from gauging spin

Aspects of screening and confinement are reassessed for a $B \wedge F$ model with topological mass with the gauging of spin. Our discussion is carried out using the gauge-invariant, but path-dependent, variables formalism. We explicitly show that the static potential profile is the sum of a Yukawa and a linear potential, leading to the confinement of static external charges. Interestingly enough, similar results are obtained in a theory of antisymmetric tensor fields that results from the condensation of topological defects as a consequence of the Julia-Toulouse mechanism.

hep-th↗

Physical Properties of the Spin Hamiltonian on Honeycomb Lattice Samples with Kekulé and Vacuum Polarization Corrections

Magnetic and thermodynamical properties of a system of spins in a honeycomb lattice, such as magnetization, magnetic susceptibility and specific heat, in a low-temperature regime are investigated by considering the effects of a Kekulé scalar exchange and QED vacuum polarization corrections to the interparticle potential. The spin lattice calculations are carried out by means of Monte Carlo simulations. We present a number of comparative plots of all the physical quantities we have considered and a detailed analysis is presented to illustrate the main features and the variation profiles of the properties with the applied external magnetic field and temperature.

cond-mat.mes-hall↗

The bosonized version of the Schwinger model in four dimensions: a blueprint for confinement?

For a $(3+1)$-dimensional generalization of the Schwinger model, we compute the interaction energy between two test charges. The result shows that the static potential profile contains a linear term leading to the confinement of probe charges, exactly as in the original model in two dimensions. We further show that the same 4-dimensional model also appears as one version of the $ B \wedge F$ models in $(3+1)$ dimensions under dualization of Stueckelberg-like massive gauge theories. Interestingly, this particular model is characterized by the mixing between a $U(1)$ potential and an Abelian $3$-form field of the type that appears in the topological sector of QCD.

hep-th↗

$(1+3)$D topological superconductors: screening and confinement in presence of external fields

Adopting the gauge-invariant and path-dependent variables formalism, we compute the interaction energy for a topological field theory describing $(1+3)$D topological superconductors in presence of external fields. As a result, in the case of a constant electric field- strength expectation value, we show that the interaction energy describes a purely screening phase, encoded in a Yukawa potential. On the other hand, in the case of a constant magnetic field-strength and for a very small Josephson coupling constant, the particle-antiparticle binding potential displays a linear term leading to the confinement of static charge probes along with a screening contribution.

hep-th↗

Ambiguity in deriving Larmor's formula from the LAD equation of motion

The power radiated by a moving charge is given by Larmor's formula which can be derived by integrating the Liénard-Wiechert potential over the whole past history of the charge. However, extracting the same result from the Lorent-Abraham-Dirac (LAD) equation of motion is problematic. This is well known for uniform proper acceleration for which case the radiation force vanishes and hence the very origin of the radiated energy is not clear, leading to an energy balance paradox. The purpose of this letter is first to evince that this problem occurs in the general case and not only for uniform acceleration. Second we show that the widely accepted treatment based on the bound field technique cannot fix the energy balance discrepancy. Indeed the related Schott term is not a legitimate four-momentum for being indefinite and not conserved.

physics.class-ph↗

Massive photons from Super and Lorentz symmetry breaking

In the context of Standard Model Extensions (SMEs), we analyse four general classes of Super Symmetry (SuSy) and Lorentz Symmetry (LoSy) breaking, leading to {observable} imprints at our energy scales. The photon dispersion relations show a non-Maxwellian behaviour for the CPT (Charge-Parity-Time reversal symmetry) odd and even sectors. The group velocities exhibit also a directional dependence with respect to the breaking background vector (odd CPT) or tensor (even CPT). In the former sector, the group velocity may decay following an inverse squared frequency behaviour. Thus, we extract a massive and gauge invariant Carroll-Field-Jackiw photon term in the Lagrangian and show that the mass is proportional to the breaking vector. The latter is estimated by ground measurements and leads to a photon mass upper limit of $10^{-19}$ eV or $2 \times 10^{-55}$ kg and thereby to a potentially measurable delay at low radio frequencies.

hep-ph↗

Remarks on the static potential driven by vacuum nonlinearities in $D=3$ models

Within the framework of the gauge-invariant, but path-dependent, variables formalism, we study the manifestations of vacuum electromagnetic nonlinearities in $D=3$ models. For this we consider both generalized Born-Infeld and Pagels-Tomboulis-like electrodynamics, as well as, an Euler-Heisenberg-like electrodynamics. We explicitly show that generalized Born-Infeld and Pagels-Tomboulis-like electrodynamics are equivalent, where the static potential profile contains a long-range (${\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle {r^2}$}}$-type) correction to the Coulomb potential. Interestingly enough, for an Euler-Heisenberg-like electrodynamics the interaction energy contains a linear potential, leading to the confinement of static charges.

hep-th↗

Aspects of screening and confinement in a topologically massive $U{\left( 1 \right)_{\cal W}} \times U{(1)_{\cal Y}}$ Chern-Simons-Higgs theory

By using the gauge-invariant but path-dependent, variables formalism, we consider a recently proposed topologically massive $U{\left( 1 \right)_{\cal W}} \times U{(1)_{\cal Y}}$ Chern-Simons-Higgs theory in $2+1$ dimensions. In particular, we inspect the impact of a Chern-Simons mixing term between two Abelian gauge fields on physical observables. We pursue our investigation by analysing the model in two different situations. In the first case, where we integrate out the massive excitation and consider an effective model for the massless field, we show that the interaction energy contains a linear term leading to the confinement of static charge probes along with a screening contribution. The second situation, where the massless field can be exactly integrated over with its constraint duly taken into account, the interesting feature is that the resulting effective model describes a purely screening phase, without any trace of a confining regime.

hep-th↗

Vortex Solutions and a Novel Role for R-parity in an N=2-Supersymmetric Model for Graphene

In a previous work, we have been able to settle Jackiw's et al. chiral gauge theory for Dirac fermions in graphene in an N=1 supersymmetric framework, using a tau3-QED prescription, defined by means of a single pair of gauge charged superfields, but without preserving a global phase symmetry associated to the electric charge. In the present work, we propose another N=1-generalisation which indeed preserves this symmetry, namely, a straightforward extension built upon a set of two pairs of (chiral) gauge-charged superfields plus an extra pair of electrically neutral superfields. We then further proceed to establish, via a dimensional reduction procedure, an N=2 extension, allowing for the identification of non-perturbative features, as we put forward Bogomol'nyi equations and obtain vortex-like solutions saturating a topologically non-trivial bound. Remarkably, the bosonic projection of the N=2 functional space onto the saturated regime analysed herewith reveals to be free from extra scalar degrees of freedom that would otherwise demand a phenomenological interpretation. The investigation of Jackiw's model within an N=2 complex superspace is also motivated by the assumption that an R-parity-like symmetry could provide a route to incorporate the global phase-fermion number invariance as an external-like symmetry of the theory, thus associating the electric charge in graphene to the complex covariance (super-)space for the N=2-D=3 setup. We prove such a hypothesis to be realisable, as we build up the model endowed with all the symmetries required to further extend Jackiw's chiral gauge theory.

hep-th↗

Self-Interacting Electromagnetic Fields and a Classical Discussion on the Stability of the Electric Charge

The present work proposes a discussion on the self-energy of charged particles in the framework of nonlinear electrodynamics. We seek magnet- ically stable solutions generated by purely electric charges whose electric and magnetic fields are computed as solutions to the Born-Infeld equa- tions. The approach yields rich internal structures that can be described in terms of the physical fields with explicit analytic solutions. This suggests that the anomalous field probably originates from a magnetic excitation in the vacuum due to the presence of the very intense electric field. In addition, the magnetic contribution has been found to exert a negative pressure on the charge. This, in turn, balances the electric repulsion, in such a way that the self-interaction of the field appears as a simple and natural classical mechanism that is able to account for the stability of the electron charge.

hep-th↗

Non-minimal Maxwell-Chern-Simons theory and the composite Fermion model

The magnetic field redefinition in Jain's composite fermion model for the fractional quantum Hall effect is shown to be effectively described by a mean-field approximation of a model containing a Maxwell-Chern-Simons gauge field non-minimally coupled to matter. Also an explicit non-relativistic limit of the non-minimal (2+1)D Dirac equation is derived.

hep-th↗