17,256 research outputs found

    Analytical BPS Maxwell-Higgs vortices

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    We have established a prescription for the calculation of analytical vortex solutions in the context of generalized Maxwell-Higgs models whose overall dynamics is controlled by two positive functions of the scalar field. We have also determined a natural constraint between these functions and the Higgs potential allowing the existence of axially symmetric Bogomol'nyi-Prasad-Sommerfield (BPS) solutions possessing finite energy. Furthermore, when the generalizing functions are chosen suitably, the nonstandard BPS equations can be solved exactly. We have studied some examples, comparing them with the usual Abrikosov-Nielsen-Olesen (ANO) solution. The overall conclusion is that the analytical self-dual vortices are well-behaved in all relevant sectors, strongly supporting the generalized models they belong themselves. In particular, our results mimic well-known properties of the usual (numerical) configurations, as localized energy density, while contributing to the understanding of topological solitons and their description by means of analytical methods.Comment: 8 pages, 4 figure

    Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering

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    We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling between fermions and Abelian gauge fields involving the CPT-even tensor (KF)μναβ(K_{F})_{\mu\nu\alpha\beta} of the standard model extension. We thus investigate its effects on the cross section of the electron-positron scattering by analyzing the process e++eμ++μe^{+}+e^{-}\rightarrow\mu^{+}+\mu^{-}. Such a study was performed for the parity-odd and parity-even nonbirefringent components of the Lorentz-violating (KF)μναβ(K_{F})_{\mu\nu\alpha\beta} tensor. Finally, by using experimental data available in the literature, we have imposed upper bounds as tight as 1012(eV)110^{-12}(eV)^{-1} on the magnitude of the CPT-even and Lorentz-violating parameters while nonminimally coupled.Comment: LaTeX2e, 06 pages, 01 figure

    Radiative generation of the CPT-even gauge term of the SME from a dimension-five nonminimal coupling term

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    In this letter we show for the first time that the usual CPT-even gauge term of the standard model extension (SME) can be radiatively generated, in a gauge invariant level, in the context of a modified QED endowed with a dimension-five nonminimal coupling term recently proposed in the literature. As a consequence, the existing upper bounds on the coefficients of the tensor (KF)(K_{F}) can be used improve the bounds on the magnitude of the nonminimal coupling, λ(KF),\lambda(K_{F}), by the factors 10510^{5} or 1025.10^{25}. The nonminimal coupling also generates higher-order derivative contributions to the gauge field effective action quadratic terms.Comment: Revtex style, two columns, 6 pages, revised final version to be published in the Physics Letters B (2013

    Coherent State Path Integrals in the Weyl Representation

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    We construct a representation of the coherent state path integral using the Weyl symbol of the Hamiltonian operator. This representation is very different from the usual path integral forms suggested by Klauder and Skagerstan in \cite{Klau85}, which involve the normal or the antinormal ordering of the Hamiltonian. These different representations, although equivalent quantum mechanically, lead to different semiclassical limits. We show that the semiclassical limit of the coherent state propagator in Weyl representation is involves classical trajectories that are independent on the coherent states width. This propagator is also free from the phase corrections found in \cite{Bar01} for the two Klauder forms and provides an explicit connection between the Wigner and the Husimi representations of the evolution operator.Comment: 23 page

    Dynamical evolution of V-type asteroids in the central main belt

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    V-type asteroids are associated with basaltic composition, and are supposed to be fragments of crust of differentiated objects. Most V-type asteroids in the main belt are found in the inner main belt, and are either current members of the Vesta dynamical family (Vestoids), or past members that drifted away. However, several V-type photometric candidates have been recently identified in the central and outer main belt. The origin of this large population of V-type objects is not well understood. Since it seems unlikely that Vestoids crossing the 3J:-1A mean-motion resonance with Jupiter could account for the whole population of V-type asteroids in the central and outer main belt, origin from local sources, such as the parent bodies of the Eunomia, and of the Merxia and Agnia asteroid families, has been proposed as an alternative mechanism. In this work we investigated the dynamical evolution of the V-type photometric candidates in the central main belt, under the effect of gravitational and non-gravitational forces. Our results show that dynamical evolution from the parent bodies of the Eunomia and Merxia/Agnia families on timescales of 2 Byr or more could be responsible for the current orbital location of most of the low-inclined V-type asteroids.Comment: 16 pages, 10 figures, 3 tables. Accepted for publication in MNRA

    Dynamical evolution and chronology of the Hygiea asteroid family

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    The asteroid (10) Hygiea is the fourth largest asteroid of the Main Belt, by volume and mass, and it is the largest member of its own family. Previous works investigated the long-term effects of close encounters with (10) Hygiea of asteroids in the orbital region of the family, and analyzed the taxonomical and dynamical properties of members of this family. In this paper we apply the high-quality SDSS-MOC4 taxonomic scheme of DeMeo and Carry (2013) to members of the Hygiea family core and halo, we obtain an estimate of the minimum time and number of encounter necessary to obtain a 3σ3\sigma (or 99.7%) compatible frequency distribution function of changes in proper aa caused by close encounters with (10) Hygiea, we study the behavior of asteroids near secular resonance configurations, in the presence and absence of the Yarkovsky force, and obtain a first estimate of the age of the family based on orbital diffusion by the Yarkovsky and YORP effects with two methods. The Hygiea family is at least 2 Byr old, with an estimated age of T=3200120+380T = 3200^{+380}_{-120} Myr and a relatively large initial ejection velocity field, according to the approach of Vokrouhlick\'{y} et al. (2006a, b). Surprisingly, we found that the family age can be shortened by \simeq 25% if the dynamical mobility caused by close encounters with (10) Hygiea is also accounted for, which opens interesting new research lines for the dynamical evolution of families associated with massive bodies. In our taxonomical analysis of the Hygiea asteroid family, we also identified a new V-type candidate: the asteroid (177904) (2005 SV5). If confirmed, this could be the fourth V-type object ever to be identified in the outer main belt.Comment: 13 page, 15 figures, and 4 table

    Desinfestação de explantes radiculares de bacurizeiro.

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    Este trabalho teve como objetivo avaliar a desinfestação de explantes radiculares de bacurizeiro para o seu estabelecimento in vitro

    Estudo de raízes de coqueiro anão verde em neossolos quartzarênicos da Fazenda São João, em Petrolina-PE.

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    O estudo foi desenvolvido em Neossolo Quartzarênico, que tem 96% de areia, 2% de silte e 2% de argila em área de plantio comercial da Fazenda São João, município de Petrolina - PE; cultivada com coqueiro anão ecotipo verde, com idade de 7 anos; plantado no espaçamento quiconcial de 7,5 x 7,5 x 7,5 metros, irrigado por microaspersão. Para irrigação utilizou-se um emissor por planta que disponibiliza uma vazão média de 40 L/h, para uma pressão de 204,00 kPa, com uma percentagem de área molhada de 48,70%. Duas plantas foram escolhidas como representativas da área para análise de distribuição de raízes no solo. Os resultados obtidos permitem estabelecer, que até a distância de 2,40 m do caule, estão concentrados 98,17% da área acumulada das raízes. No que se refere à profundidade e até a distância de 2,40 m, menos de 6% das raízes estão abaixo de 1,20 m. As raízes mais compridas e as de maior área estão localizadas entre 0,20 e 0,60 m de profundidade numa sequência crscente até a distância de 1,80 m
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