On the dimensional dependence of duality groups for massive p-forms

We study the soldering formalism in the context of abelian p-form theories. We develop further the fusion process of massless antisymmetric tensors of different ranks into a massive p-form and establish its duality properties. To illustrate the formalism we consider two situations. First the soldering mass generation mechanism is compared with the Higgs and Julia-Toulouse mechanisms for mass generation due to condensation of electric and magnetic topological defects. We show that the soldering mechanism interpolates between them for even dimensional spacetimes, in this way confirming the Higgs/Julia-Toulouse duality proposed by Quevedo and Trugenberger \cite{QT} a few years ago. Next, soldering is applied to the study of duality group classification of the massive forms. We show a dichotomy controlled by the parity of the operator defining the symplectic structure of the theory and find their explicit actions.Comment: Reference [8] has been properly place

Steady-state entanglement between distant quantum dots in photonic crystal dimers

We show that two spatially separated semiconductor quantum dots under resonant and continuous-wave excitation can be strongly entangled in the steady-state, thanks to their radiative coupling by mutual interaction through the normal modes of a photonic crystal dimer. We employ a quantum master equation formalism to quantify the steady-state entanglement by calculating the system {\it negativity}. Calculations are specified to consider realistic semiconductor nanostructure parameters for the photonic crystal dimer-quantum dots coupled system, determined by a guided mode expansion solution of Maxwell equations. Negativity values of the order of 0.1 ($20\%$ of the maximum value) are shown for interdot distances that are larger than the resonant wavelength of the system. It is shown that the amount of entanglement is almost independent of the interdot distance, as long as the normal mode splitting of the photonic dimer is larger than their linewidths, which becomes the only requirement to achieve a local and individual qubit addressing. Considering inhomogeneously broadened quantum dots, we find that the steady-state entanglement is preserved as long as the detuning between the two quantum dot resonances is small when compared to their decay rates. The steady-state entanglement is shown to be robust against the effects of pure dephasing of the quantum dot transitions. We finally study the entanglement dynamics for a configuration in which one of the two quantum dots is initially excited and find that the transient negativity can be enhanced by more than a factor of two with respect to the steady-state value. These results are promising for practical applications of entangled states at short time scales.Comment: 10 pages, 7 figure

On duality of the noncommutative extension of the Maxwell-Chern-Simons model

We study issues of duality in 3D field theory models over a canonical noncommutative spacetime and obtain the noncommutative extension of the Self-Dual model induced by the Seiberg-Witten map. We apply the dual projection technique to uncover some properties of the noncommutative Maxwell-Chern-Simons theory up to first-order in the noncommutative parameter. A duality between this theory and a model similar to the ordinary self-dual model is estabilished. The correspondence of the basic fields is obtained and the equivalence of algebras and equations of motion are directly verified. We also comment on previous results in this subject.Comment: Revtex, 9 pages, accepted for publication PL

Massive scalar field near a cosmic string

The $\zeta$ function of a massive scalar field near a cosmic string is computed and then employed to find the vacuum fluctuation of the field. The vacuum expectation value of the energy-momentum tensor is also computed using a point-splitting approach. The obtained results could be useful also for the case of self-interacting scalar fields and for the finite-temperature Rindler space theory.Comment: 15 pages, standard LaTeX, no figures. Reference [14] correcte

Carbon nanotube: a low-loss spin-current waveguide

We demonstrate with a quantum-mechanical approach that carbon nanotubes are excellent spin-current waveguides and are able to carry information stored in a precessing magnetic moment for long distances with very little dispersion and with tunable degrees of attenuation. Pulsed magnetic excitations are predicted to travel with the nanotube Fermi velocity and are able to induce similar excitations in remote locations. Such an efficient way of transporting magnetic information suggests that nanotubes are promising candidates for memory devices with fast magnetization switchings

Group theory analysis of electrons and phonons in N-layer graphene systems

In this work we study the symmetry properties of electrons and phonons in graphene systems as function of the number of layers. We derive the selection rules for the electron-radiation and for the electron-phonon interactions at all points in the Brillouin zone. By considering these selection rules, we address the double resonance Raman scattering process. The monolayer and bilayer graphene in the presence of an applied electric field are also discussed.Comment: 8 pages, 6 figure

Comparison of a rapid test and an automated method for faecal calprotectin measurement

n/aWe acknowledge Arium Diagnostics Systems LDA (Bühlmann Laboratories AG representative in Portugal) for its support in providing fCAL® Turbo tests and controls. Arium did not play any role in study design, execution, analysis or interpretation of the data

Consequências da redução de espaçamentos entre as linhas e entre as plantas na linha de plantio sobre os componentes vegetativos de cafeeiros (Coffea arabica L.) cultivar Catuaí.

O experimento foi instalado na Fazenda Experimental da EPAMIG em Machado, sul de Minas Gerais, em 1992, com o objetivo de avaliar as conseqüências da redução de espaçamentos entre as linhas e entre as plantas na linha de plantio sobre a produção e a fenologia do cafeeiro. O delineamento experimental utilizado foi um fatorial 4 x 3 com parcela subdividida, sendo quatro distâncias entre as linhas (2,0? 2,5? 3,0 e 3,5 m) e três distâncias entre as plantas na linha de plantio (0,5? 0,75? 1,0 m), e totalizando 12 tratamentos dispostos em blocos ao acaso em três repetições. Em julho de 2002, logo após a colheita e antes da primeira recepa, foram avaliadas as características relativas à arquitetura dos cafeeiros (altura da planta, diâmetro da copa, altura dos ramos plagiotrópicos baixeiros e diâmetro do caule). O adensamento entre linhas proporciona plantas mais altas, com inserção dos primeiros ramos plagiotrópicos mais altos, menores comprimento e diâmetro da copa. O adensamento entre linhas não afeta o diâmetro do caule. Já o adensamento das plantas na linha de plantio linha proporciona também plantas mais altas e com inserção dos primeiros ramos plagiotrópicos mais altos, não influencia o comprimento da copa e apresenta diâmetros da copa e do caule menores