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P. Castelo Ferreira

Publications and source records attributed to P. Castelo Ferreira.

At least 37 records · Page 2Linked to original sources
arXiv2007

Pseudo-Photon Radiative Corrections in Non-Regular Backgrounds

Extended $U_e(1)\times U_g(1)$ electromagnetism containing both a photon and a pseudo-photon is introduced at variational level and is justified by the violation of the Bianchi identities in conceptual systems, either in the presence of magnetic monopoles or non-regular external fields, not being accounted by the standard Maxwell action. It is shown that in the perturbative quantum field theory regimes there are observable consequences both for the magnetic momenta and second order vacuum polarization radiative corrections in the presence of non-regular strong electromagnetic fields (e.g. rotating magnetic fields).

hep-th↗
arXiv2007

A Pseudo-Photon in Non-Trivial Background Fields

We show that in the presence of external fields for which either $\dot{\vb{B}}^{\mathrm{ext}}\neq 0$ or $\nabla\times\vb{E}^{\mathrm{ext}}\neq 0$ it is not possible to derive the classical Maxwell equations from an action with only one gauge field. We suggest that one possible solution is to consider a second physical pseudo-vector gauge field $C$. The action for this theory is originally motivated by the inclusion of magnetic monopoles. These particles play no role in this work and our argument is only based in, that the violation of the Bianchi identities, cannot be accounted at the action level with only the standard gauge field. We give a particular example for a periodic rotating external magnetic field. Our construction holds that at classical level both the vector and pseudo-vector gauge fields $A$ and $C$ are regular. We compare pseudo-photon with paraphoton (graviphoton) theories concluding that, besides the mechanisms of gauge symmetry breaking already studied, the Bianchi identities violation are a crucial difference between both theories. We also show that, due to Dirac's quantization condition, at quantum field theory level the effects due to pseudo-photons and photons can be distinguished by the respective contributions to the magnetic moment of fermions and vacuum polarization. These effects may be relevant in astrophysical environments, namely close and inside neutron stars and magnetars. [Erratum: The construction in this work must, at most, be considered as a conceptual system or toy model. Are discussed systems where the results may have relevance.]

hep-ph↗
arXiv2007

U_e(1)xU_g(1) Actions in 2+1-Dimensions: Full Vectorial Electric and Magnetic Fields

It is considered a dimensional reduction of Ue(1)xUg(1) 3+1-dimensional electromagnetism with a gauge field (photon) and a pseudo-vector gauge field (pseudo-photon) to 2+1-dimensions. In the absence of boundary effects, the quantum structure is maintained, while when boundary effects are considered, as have been previously studied, a cross Chern-Simons term between both gauge fields is present, which accounts for topological effects and changes the quantum structure of the theory. Our construction maintains the dimensional reduced action invariant under parity (P) and time-inversion (T). We show that the theory has two massive degrees of freedom, corresponding to the longitudinal modes of the photon and of the pseudo-photon and briefly discuss the quantization procedures of the theory in the topological limit (wave functional quantization) and perturbative limit (an effective dynamical current theory), pointing out directions to solve the constraints and deal with the negative energy contributions from pseudo-photons. We recall that the physical interpretation of the fields in the planar system is new and is only meaningful in the context of Ue(1)xUg(1) electromagnetism. In this work it is shown that all the six electromagnetic vectorial fields components are present in the dimensional reduced theory and that, independently of the embedding of the planar system, can be described in terms of the two gauge fields only. As far as the author is aware it is the first time that such a construction is fully justified, thus allowing a full vectorial treatment at variational level of electromagnetism in planar systems.

hep-th↗
arXiv2007

Effective Electric and Magnetic Local Actions for Ue(1)xUg(1) Electromagnetism: Hodge Duality and Zero-Field Equation

It is considered a mechanism of dynamical symmetry breaking for extended Ue(1)xUg(1) containing, one vector gauge field 'A' (photon) and one pseudo-vector gauge field 'C' (pseudo-photon). By choosing a particular solution of the equations of motion we obtain a functional description of either field in terms of the other one. In this way we obtain non-trivial configurations 'C=C(A)' or 'A=A(C)' such that, in the effective broken theories containing only one gauge field, the usual field discontinuities in the presence of both electric and magnetic monopoles are absent. These fields regularity is achieved through corrections, inherited from the unbroken theory, to the standard definitions of electromagnetic fields and four-currents. Based in these results we also demonstrate non-triviality of the unbroken theory, in the presence of both electric and magnetic four-currents, there are no trivial solutions compatible with the equations of motion for both fields. Moreover we demonstrate that, although in complete agreement with the Maxwell equations, extended 'Ue(1)xUg(1)' electromagnetism is not equivalent to the standard variational 'U(1)' Maxwell electromagnetism. We further show that the unbroken theory is invariant under a combination of Hodge dualities that has as self-dual point the field configuration corresponding to the zero-field equation. In addition this condition has the particularity of being the only configuration compatible with the mechanism of dynamical symmetry breaking proposed here that is also gauge invariant in the unbroken theory. These characteristics justify the zero-field equation as being a preferred configuration.

hep-th↗
arXiv2007

Higher Harmonics in Non-Linear Vacuum from QED Effects Without Low Mass Intermediate Particles

We show that in the presence of a slowly rotating strong transverse magnetic field there is an infinite spectrum of harmonic wave functions $A_n$ due to the first order QED correction (in $α^2$) given by the Euler-Heisenberg Lagrangian. The frequency shifts are integer multiples $\pm ω_0 n$ of the magnetic field angular frequency rotation $ω_0=2πν_m$ and the several modes $n$ are coupled to the nearest harmonics $n\pm 1$. This is a new effect due to QED vacuum fluctuations, not exploit before, that can explain, both qualitatively and quantatively, the recent experimental results of the PVLAS collaboration without the need of a low mass intermediate particle, hence dismiss the recent claim of the discovery of the axion. [Erratum: The PVLAS signal cannot be explained by this mechanism.]

hep-ph↗
arXiv2006

Explicit Actions for Electromagnetism with Two Gauge Fields with Only one Electric and one Magnetic Physical Fields

We extend the work of Mello et al. based in Cabbibo and Ferrari concerning the description of electromagnetism with two gauge fields from a variational principle, i.e. an action. We provide a systematic independent derivation of the allowed actions which have only one magnetic and one electric physical fields and are invariant under the discrete symmetries $P$ and $T$. We conclude that neither the Lagrangian, nor the Hamiltonian, are invariant under the electromagnetic duality rotations. This agrees with the weak-strong coupling mixing characteristic of the duality due to the Dirac quantization condition providing a natural way to differentiate dual theories related by the duality rotations (the energy is not invariant). Also the standard electromagnetic duality rotations considered in this work violate both $P$ and $T$ by inducing Hopf terms (theta terms) for each sector and a mixed Maxwell term. The canonical structure of the theory is briefly addressed and the 'magnetic' gauge sector is interpreted as a ghost sector.

hep-th↗
arXiv2006

Rotating Electric Classical Solutions of 2+1 D U(1) Einstein Maxwell Chern-Simons

We study electric stationary radial symmetric classical solutions of the U(1) Einstein Maxwell Chern-Simons theory coupled to a gravitational massless scalar field with a cosmological constant in 2+1 dimensions. Generic aspects of the theory are discussed at an introductory level. We study solutions for both negative sign (standard) and positive sign (ghost) of the gauge sector concluding that although the expressions for the solutions are the same, the constants as well as the physics change significantly. It is found a rotating electric point particle. For the standard sign and specific values of the parameters corresponding to solutions with positive mass the singularity is dressed (in the sense that itself constitutes an horizon). The space-time curvatures can be both positive or negative depending on the dominance of the scalar or topologically massive matter. The Chern-Simons term is responsible for interesting features, besides only allowing for rotating solutions, it imposes restrictive bounds on the cosmological constant $Λ$ such that it belongs to a positive interval and is switch on and off by the topological mass $m^2$. Furthermore the charge, angular momentum and mass of the particle solution are expressed uniquely as functions of the ratio between the cosmological constant and the topological mass squared $x=Λ/m^2$. The main drawback of our particle solution is that the mass is divergent. Our background is a rotating flat space without angular deficit. We briefly discuss parity and time-inversion violation by the Chern-Simons term which is explicit in the solutions obtained, their angular momentum only depends on the relative sign between the Chern-Simons term and the Maxwell term. Trivial solutions are briefly studied holding non-singular extended configurations.

hep-th↗
arXiv2006

From U(1) Maxwell Chern-Simons to Azbel-Hofstadter: Testing Magnetic Monopoles and Gravity to $\sim 10^{-15}$\textit{m}?

It is built a map between an Abelian Topological Quantum Field Theory, $2+1D$ compact U(1) gauge Maxwell Chern-Simons Theory and the nonrelativistic quantum mechanics Azbel-Hofstadter model of Bloch electrons. The $U_q(sl_2)$ quantum group and the magnetic translations group of the Azbel-Hofstadter model correspond to discretized subgroups of U(1) with linear gauge parameters. The magnetic monopole confining and condensate phases in the Topological Quantum Field Theory are identified with the extended (energy bands) and localized (gaps) phases of the Bloch electron. The magnetic monopole condensate is associated, at the nonrelativistic level, with gravitational white holes due to deformed classical gauge fields. These gravitational solutions render the existence of finite energy pure magnetic monopoles possible. This mechanism constitutes a dynamical symmetry breaking which regularizes the solutions on those localized phases allowing physical solutions of the Shrödinger equation which are chains of electron filaments connecting several monopole-white holes.To test these results would be necessary a strong external magnetic field $B\sim 5 T$ at low temperature $T<1 K$. To be accomplished, it would test the existence of magnetic monopoles and classical gravity to a scale of $\sim 10^{-15}$ \textit{meters}, the dimension of the monopole-white hole. A proper discussion of such experiment is out of the scope of this theoretical work.

hep-th↗
arXiv2006

Why Randall-Sundrum Scenarious are not Compatible with an Orbifolded Fifth Dimension

We show the (already known) fact that Randall-Sundrum scenarious although compatible with a ${\mathbb{Z}}_2$ orbifold symmetry cannot hold regularity of the fields at the orbifold planes in the absence of boundary actions and respective jumps of the fields. This makes the models mathematical inconsistence and invalidate the inclusion of such models in a higher dimensional theory such as string theory. For completeness we point out some directions already in the literature and in progress.

hep-th↗
arXiv2003

D-Branes in Topological Membranes

It is shown how two-dimensional states corresponding to D-branes arise in orbifolds of topologically massive gauge and gravity theories. Brane vertex operators naturally appear in induced worldsheet actions when the three-dimensional gauge theory is minimally coupled to external charged matter and the orbifold relations are carefully taken into account. Boundary states corresponding to D-branes are given by vacuum wavefunctionals of the gauge theory in the presence of the matter, and their various constraints, such as the Cardy condition, are shown to arise through compatibility relations between the orbifold charges and bulk gauge invariance. We show that with a further conformally-invariant coupling to a dynamical massless scalar field theory in three dimensions, the brane tension is naturally set by the bulk mass scales and arises through dynamical mechanisms. As an auxilliary result, we show how to describe string descendent states in the three-dimensional theory through the construction of gauge-invariant excited wavefunctionals.

hep-th↗
arXiv2002

Conformal Orbifold Partition Functions from Topologically Massive Gauge Theory

We continue the development of the topological membrane approach to open and unoriented string theories. We study orbifolds of topologically massive gauge theory defined on the geometry $[0,1]\timesΣ$, where $Σ$ is a generic compact Riemann surface. The orbifold operations are constructed by gauging the discrete symmetries of the bulk three-dimensional field theory. Multi-loop bosonic string vacuum amplitudes are thereby computed as bulk correlation functions of the gauge theory. It is shown that the three-dimensional correlators naturally reproduce twisted and untwisted sectors in the case of closed worldsheet orbifolds, and Neumann and Dirichlet boundary conditions in the case of open ones. The bulk wavefunctions are used to explicitly construct the characters of the underlying extended Kac-Moody group for arbitrary genus. The correlators for both the original theory and its orbifolds give the expected modular invariant statistical sums over the characters.

hep-th↗
arXiv2001

Open and Unoriented Strings from Topological Membrane - I. Prolegomena

We study open and unoriented strings in a Topological Membrane (TM) theory through orbifolds of the bulk 3D space. This is achieved by gauging discrete symmetries of the theory. Open and unoriented strings can be obtained from all possible realizations of $C$, $P$ and $T$ symmetries. The important role of $C$ symmetry to distinguish between Dirichlet and Neumman boundary conditions is discussed in detail.

hep-th↗
arXiv2000

Phase Diagrams of the Harper Map and the Golden Staircase

We present phase diagrams of the Harper map, which is equivalent to the problem of Bloch electrons in a uniform magnetic field (Azbel-Hofstadter model). We consider the cases where the magnetic flux $ω$ assumes either the continued fraction approximations towards the golden mean or the golden mean itself. The phase diagrams for rational values of $ω$ show a finite number of Arnol'd tongues of localized electronic states with rational winding numbers and regions of extended phases in between them. For the particular case of $ω= \frac{\sqrt{5}-1}{2}$, we find an infinite number of Arnol'd tongues of localized phases with extended phases in between. In this case, the study of the winding number gives rise to a Golden Staircase, where the plateaux represent localized phases with winding numbers equal to sums of powers of the golden mean. We also present evidence of the existence of an infinite number of strange nonchaotic attractors for $ε=1$ in points analogous to critical points in the pressure-temperature phase diagram of the water.

cond-mat.dis-nn↗