Jakson M. Fonseca

All orders renormalizability of a Lorentz and CPT violating quantum electrodynamics

Renormalizability of the (minimal) single-fermion QED extension is investigated at all orders of perturbation theory in the framework of algebraic renormalization, a regularization-independent method. Relative to the standard QED, new structures that could lead to gauge anomalies are identified. Nevertheless, even if the anomaly coefficients fail to vanish in the general case, they shall be absent provided we require invariance of the action under

Scattering of charge carriers in graphene induced by topological defects

C

Topological magnetic solitons on a paraboloidal shell

and/or

Testing CPT- and Lorentz-odd electrodynamics with waveguides

PT

Emission and absorption of photons and the black-body spectrum in Lorentz-odd electrodynamics

transformations. Stability is also verified in this case, hence full renormalizability is attained.

Stability of skyrmions on curved surfaces in the presence of a magnetic field

We study the scattering of graphene quasiparticles by topological defects, represented by holes, pentagons and heptagons. For holes, we found that at low concentration they give a negligible contribution to the resistivity. Whenever pentagons or heptagons are introduced we realize that a fermionic current is scattered by defects.

Geometrically induced electric polarization in conical topological insulators

Abstract We study the influence of curvature on the exchange energy of skyrmions and vortices on a paraboloidal surface. It is shown that such structures appear as excitations of the Heisenberg model, presenting topological stability, unlike what happens on other simply-connected geometries such as pseudospheres. We also show that the skyrmion width depends on the geometrical parameters of the paraboloid. The presence of a magnetic field leads to the appearance of 2 π -skyrmions, introducing a new characteristic length into the system. Regarding vortices, the geometrical parameters of the paraboloid play an important role in the exchange energy of this excitation.

Curvature-induced changes in the magnetic energy of vortices and skyrmions in paraboloidal nanoparticles

We study CPT- and Lorentz-odd electrodynamics described by the Standard Model Extension. Its radiation is confined to the geometry of a hollow conductor waveguide open along the z-axis. In a special class of reference frames, with vanishing both 0-th and z components of the background field, (kAF)μ, we determine a number of huge and macroscopically detectable effects on the confined waves spectra, compared to standard results. Particularly, if (kAF)μ points along the x (or y) direction, only transverse electric modes, with Ez = 0, should be observed propagating throughout the guide, while all the transverse magnetic, Bz = 0, are absent. Such a strong mode suppression makes waveguides quite suitable to probe these symmetry violations using a simple and easily reproducible apparatus.

Bound-states and polarized charged zero modes in three-dimensional topological insulators induced by a magnetic vortex

Abstract We study emission and absorption of radiation by non-relativistic electrons within the framework of a Lorentz-breaking electrodynamics in ( 3 + 1 ) dimensions. We have realised that Planck-type law acquires extra terms proportional to the violating parameters: For the CPT-odd model, the leading extra terms appear to be linear or quadratic in these violating parameters according to the background vector is parallel or perpendicular to the photon wave-vector. In the CPT-even case a linear correction shows up. Besides these deviations in the black-body spectra, those violations may be also probed through a difference in the photon mean occupation number for the two modes. Our results also indicate that such violations are better probed at very low temperatures, where their effects on the thermal spectra are largely enhanced.

Circular single domains in hemispherical Permalloy nanoclusters

Abstract We study the stability and energetics associated to skyrmions appearing as excitations on curved surfaces. Using a continuum model we show that the presence of cylindrically radial and azimuthal fields destabilize the skyrmions that appear in the absence of an external field. Weak fields generate fractional skyrmions while strong magnetic fields yield stable 2 π -skyrmions, which have their widths diminished by the magnetic field strength. Under azimuthal fields vortex appears as stable state on the curved surface.