594 research outputs found

    Maxwell-Chern-Simons vortices in a CPT-odd Lorentz-violating Higgs Electrodynamics

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    We have studied BPS vortices in a CPT-odd and Lorentz-violating Maxwell-Chern-Simons-Higgs (MCSH) electrodynamics attained from the dimensional reduction of the Carroll-Field-Jackiw-Higgs model. The Lorentz-violating parameter induces a pronounced behavior at origin (for the magnetic/electric fields and energy density) which is absent in the MCSH vortices. For some combination of the Lorentz-violating coefficients there always exist a sufficiently large winding number n0n_{0} such that for all % |n|\geq |n_{0}| the magnetic field flips its signal, yielding two well defined regions with opposite magnetic flux. However, the total magnetic flux remains quantized and proportional to the winding number.Comment: Revtex style, 8 page

    Evaluation of effective resistances in pseudo-distance-regular resistor networks

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    In Refs.[1] and [2], calculation of effective resistances on distance-regular networks was investigated, where in the first paper, the calculation was based on the stratification of the network and Stieltjes function associated with the network, whereas in the latter one a recursive formula for effective resistances was given based on the Christoffel-Darboux identity. In this paper, evaluation of effective resistances on more general networks called pseudo-distance-regular networks [21] or QD type networks \cite{obata} is investigated, where we use the stratification of these networks and show that the effective resistances between a given node such as α\alpha and all of the nodes β\beta belonging to the same stratum with respect to α\alpha (Rαβ(m)R_{\alpha\beta^{(m)}}, β\beta belonging to the mm-th stratum with respect to the α\alpha) are the same. Then, based on the spectral techniques, an analytical formula for effective resistances Rαβ(m)R_{\alpha\beta^{(m)}} such that Lαα1=Lββ1L^{-1}_{\alpha\alpha}=L^{-1}_{\beta\beta} (those nodes α\alpha, β\beta of the network such that the network is symmetric with respect to them) is given in terms of the first and second orthogonal polynomials associated with the network, where L1L^{-1} is the pseudo-inverse of the Laplacian of the network. From the fact that in distance-regular networks, Lαα1=Lββ1L^{-1}_{\alpha\alpha}=L^{-1}_{\beta\beta} is satisfied for all nodes α,β\alpha,\beta of the network, the effective resistances Rαβ(m)R_{\alpha\beta^{(m)}} for m=1,2,...,dm=1,2,...,d (dd is diameter of the network which is the same as the number of strata) are calculated directly, by using the given formula.Comment: 30 pages, 7 figure

    Photon Orbital Angular Momentum and Mass in a Plasma Vortex

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    We analyse the Anderson-Higgs mechanism of photon mass acquisition in a plasma and study the contribution to the mass from the orbital angular momentum acquired by a beam of photons when it crosses a spatially structured charge distribution. To this end we apply Proca-Maxwell equations in a static plasma with a particular spatial distribution of free charges, notably a plasma vortex, that is able to impose orbital angular momentum (OAM) onto light. In addition to the mass acquisition of the conventional Anderson-Higgs mechanism, we find that the photon acquires an additional mass from the OAM and that this mass reduces the Proca photon mass.Comment: Four pages, no figures. Error corrections, improved notation, refined derivation

    ExploreNEOs I: Description and first results from the Warm Spitzer NEO Survey

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    We have begun the ExploreNEOs project in which we observe some 700 Near Earth Objects (NEOs) at 3.6 and 4.5 microns with the Spitzer Space Telescope in its Warm Spitzer mode. From these measurements and catalog optical photometry we derive albedos and diameters of the observed targets. The overall goal of our ExploreNEOs program is to study the history of near-Earth space by deriving the physical properties of a large number of NEOs. In this paper we describe both the scientific and technical construction of our ExploreNEOs program. We present our observational, photometric, and thermal modeling techniques. We present results from the first 101 targets observed in this program. We find that the distribution of albedos in this first sample is quite broad, probably indicating a wide range of compositions within the NEO population. Many objects smaller than one kilometer have high albedos (>0.35), but few objects larger than one kilometer have high albedos. This result is consistent with the idea that these larger objects are collisionally older, and therefore possess surfaces that are more space weathered and therefore darker, or are not subject to other surface rejuvenating events as frequently as smaller NEOs.Comment: AJ in pres

    ExploreNEOs. II. The Accuracy of the Warm Spitzer Near-Earth Object Survey

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    We report on results of observations of near-Earth objects (NEOs) performed with the NASA Spitzer Space Telescope as part of our ongoing (2009-2011) Warm Spitzer NEO survey ("ExploreNEOs"), the primary aim of which is to provide sizes and albedos of some 700 NEOs. The emphasis of the work described here is an assessment of the overall accuracy of our survey results, which are based on a semi-empirical generalized model of asteroid thermal emission. The NASA Spitzer Space Telescope has been operated in the so-called Warm Spitzer mission phase since the cryogen was depleted in 2009 May, with the two shortest-wavelength channels, centered at 3.6 μm and 4.5 μm, of the Infrared Array Camera continuing to provide valuable data. The set of some 170 NEOs in our current Warm Spitzer results catalog contains 28 for which published taxonomic classifications are available, and 14 for which relatively reliable published diameters and albedos are available. A comparison of the Warm Spitzer results with previously published results ("ground truth"), complemented by a Monte Carlo error analysis, indicates that the rms Warm Spitzer diameter and albedo errors are ±20% and ±50%, respectively. Cases in which agreement with results from the literature is worse than expected are highlighted and discussed; these include the potential spacecraft target 138911 2001 AE_2. We confirm that 1.4 appears to be an appropriate overall default value for the relative reflectance between the V band and the Warm Spitzer wavelengths, for use in correction of the Warm Spitzer fluxes for reflected solar radiation

    Monitoramento populacional do Diaphorina citri KUWAYAMA, 1908 (HEMIPTERA: LIVIIDAE), em novas fronteiras citrícolas da Bahia: Barreiras e Juazeiro.

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    A produção de citros no Brasil é afetada por várias doenças e pragas, entre elas a Huanglongbing (HLB), causada por Candidatus Liberibacter spp. e transmitida pelo psilídeo Diaphorina citri. Todas as variedades cítricas são atacadas pelo HLB e, devido ao difícil manejo desta doença, ela é considerada como a mais destrutiva para a cultura dos citros. A planta ornamental Murraya paniculata conhecida como murta, também é hospedeira da bactéria e do vetor

    ExploreNEOs. III. Physical Characterization of 65 Potential Spacecraft Target Asteroids

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    Space missions to near-Earth objects (NEOs) are being planned at all major space agencies, and recently a manned mission to an NEO was announced as a NASA goal. Efforts to find and select suitable targets (plus backup targets) are severely hampered by our lack of knowledge of the physical properties of dynamically favorable NEOs. In particular, current mission scenarios tend to favor primitive low-albedo objects. For the vast majority of NEOs, the albedo is unknown. Here we report new constraints on the size and albedo of 65 NEOs with rendezvous Δv <7 km s^(–1). Our results are based on thermal-IR flux data obtained in the framework of our ongoing (2009-2011) ExploreNEOs survey using NASA's "Warm-Spitzer" space telescope. As of 2010 July 14, we have results for 293 objects in hand (including the 65 low-Δv NEOs presented here); before the end of 2011, we expect to have measured the size and albedo of ~700 NEOs (including probably ~160 low-Δv NEOs). While there are reasons to believe that primitive volatile-rich materials are universally low in albedo, the converse need not be true: the orbital evolution of some dark objects likely has caused them to lose their volatiles by coming too close to the Sun. For all our targets, we give the closest perihelion distance they are likely to have reached (using orbital integrations from Marchi et al. 2009) and corresponding upper limits on the past surface temperature. Low-Δv objects for which both albedo and thermal history may suggest a primitive composition include (162998) 2001 SK162, (68372) 2001 PM9, and (100085) 1992 UY4
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