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Carvalho-Santos V.L.,Instituto Federal Of Educacao | Dandoloff R.,Cergy-Pontoise University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2012

We study the nonlinear σ-model in an external magnetic field applied on curved surfaces with rotational symmetry. The Euler-Lagrange equations derived from the Hamiltonian yield the double sine-Gordon equation (DSG) provided the magnetic field is tuned with the curvature of the surface. A 2π skyrmion appears like a solution for this model and surface deformations are predicted at the sector where the spins point in the opposite direction to the magnetic field. We also study some specific examples by applying the model on three rotationally symmetric surfaces: the cylinder, the catenoid and the hyperboloid. © 2012 Elsevier B.V. Source


Alencar I.D.C.C.,Instituto Federal Of Educacao | Azevedo C.O.,Federal University of Espirito Santo
Systematic Entomology | Year: 2013

Epyrini (Epyrinae) are the largest and morphologically most diverse group within Bethylidae. Evans' conception of Epyrini induces misclassification of several taxa and their diagnostic features, such as median lobe of clypeus projected, and fovea in lateroposterior angle of propodeal disc, are insufficient to place species in the tribe. No previous comprehensive cladistic study has recovered Epyrini as a clade, and no synapomorphies are reported for the tribe, suggesting that the group is artificial. We infer a phylogeny based on 391 informative morphological characters for 42 terminal taxa (31 ingroup, 11 outgroup). Monophyly of Epyrini is supported by a petiole with fused root and body as an autapomorphy. Anisepyris Kieffer, Laelius Ashmead, Holepyris Kieffer, Formosiepyris Terayama, Disepyris Kieffer, Bakeriella Kieffer and Trachepyris Kieffer were retrieved as monophyletic. Epyris Westwood and Chlorepyris Kieffer are paraphyletic. The addition of new characters was essential to define Epyrini, and the ventral region of the mesosoma, petiole and male genitalia may help to better understand genera and species limits. All resulting trees indicate that Epyrinae are polyphyletic. Tribes Epyrini and Sclerodermini are revalidated to subfamily status. © 2012 The Royal Entomological Society. Source


Cruz W.T.,Instituto Federal Of Educacao | Gomes A.R.,Federal University of Maranhao | Almeida C.A.S.,Federal University of Ceara
European Physical Journal C | Year: 2011

In this work we investigate the issue of fermion localization and resonances in (4,1)-deformed branes constructed with one scalar field coupled with gravity. Such models provide us branes with internal structures that turns the gravitational interaction more effective for fermions aside the brane, increasing their lifetime. The coupling between the scalar field and spinors is a necessary condition for fermions to be localized on such branes. After performing a chiral decomposition of the five-dimensional spinor we found resonances with both chiralities. The correspondence between the spectra for left and right chirality is guaranteed and Dirac fermions are realized on the brane. © Springer-Verlag / Società Italiana di Fisica 2011. Source


Cruz W.T.,Instituto Federal Of Educacao | Lima A.R.P.,University da Integracao Internacional da Lusofonia Afro Brasileira | Almeida C.A.S.,Federal University of Ceara
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We present new results on the localization of gauge fields in thick brane models. The four-dimensional observable universe is considered to be a topological defect which is generated by two scalar fields coupled with gravity embedded in a five-dimensional space-time. Like other thick brane models, the Bloch brane setup is not capable of supporting gauge field localization. In order to circumvent this problem we include the dilaton field and, as a result, obtain normalizable solutions. In addition, by writing the equations of motion as Schrödinger-like equations, we have found new kinds of resonances in the massive spectrum which appear also for heavy modes. This is in sharp contrast to what is commonly found in previous analog studies, where only light modes become resonant. At specific energies, the wave solutions exhibit very high amplitudes within the membrane. The influence of the dilaton coupling and of the internal structure on the resonant modes are also discussed. © 2013 American Physical Society. Source


Maluf R.V.,Federal University of Ceara | Silva J.E.G.,Federal University of Ceara | Cruz W.T.,Instituto Federal Of Educacao | Almeida C.A.S.,Federal University of Ceara
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

In this work, we study the modified Dirac equation in the framework of very special relativity (VSR). The low-energy regime is accessed and the nonrelativistic Hamiltonian is obtained. It turns out that this Hamiltonian is similar to that achieved from the Standard Model Extension (SME) via coupling of the spinor field to a Lorentz-violating term, but new features arise inherited from the non-local character of the VSR. In addition, the implications of the VSR-modified Lorentz symmetry on the spectrum of a hydrogen atom are determined by calculating the first-order energy corrections in the context of standard quantum mechanics. Among the results, we highlight that the modified Hamiltonian provides non-vanishing corrections which lift the degeneracy of the energy levels and allow us to find an upper bound upon the VSR-parameter. © 2014 The Authors. Source

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