15,023 research outputs found

    General scalar products in the arbitrary six-vertex model

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    In this work we use the algebraic Bethe ansatz to derive the general scalar product in the six-vertex model for generic Boltzmann weights. We performed this calculation using only the unitarity property, the Yang-Baxter algebra and the Yang-Baxter equation. We have derived a recurrence relation for the scalar product. The solution of this relation was written in terms of the domain wall partition functions. By its turn, these partition functions were also obtained for generic Boltzmann weights, which provided us with an explicit expression for the general scalar product.Comment: 24 page

    Polarization-selective excitation of N-V centers in diamond

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    The nitrogen-vacancy (N-V) center in diamond is promising as an electron spin qubit due to its long-lived coherence and optical addressability. The ground state is a spin triplet with two levels (ms=±1m_s = \pm 1) degenerate at zero magnetic field. Polarization-selective microwave excitation is an attractive method to address the spin transitions independently, since this allows operation down to zero magnetic field. Using a resonator designed to produce circularly polarized microwaves, we have investigated the polarization selection rules of the N-V center. We first apply this technique to N-V ensembles in [100] and [111]-oriented samples. Next, we demonstrate an imaging technique, based on optical polarization dependence, that allows rapid identification of the orientations of many single N-V centers. Finally, we test the microwave polarization selection rules of individual N-V centers of known orientation

    f [N pi N]: from quarks to the pion derivative coupling

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    We study the N pi N coupling, in the framework of a QCD-inspired confining Nambu-Jona-Lasinio model. A simple relativistic confining and instantaneous quark model is reviewed. The Salpeter equation for the nucleon and the boosted pion is solved. The f [n pi n] and f[n pi Delta] couplings are calculated and they turn out to be reasonably good. The sensibility of f[n pi n] and f[n pi Delta] to confinement, chiral symmetry breaking and Lorentz invariance is briefly discussed.Comment: 30 pages in LaTex RevTex, 6 postscript figure

    Inducing energy gaps in graphene monolayer and bilayer

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    In this paper we propose a mechanism for the induction of energy gaps in the spectrum of graphene and its bilayer, when both these materials are covered with water and ammonia molecules. The energy gaps obtained are within the range 20-30 meV, values compatible to those found in experimental studies of graphene bilayer. We further show that the binding energies are large enough for the adsorption of the molecules to be maintained even at room temperature

    Noncommutative fields in three dimensions and mass generation

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    We apply the noncommutative fields method for gauge theory in three dimensions where the Chern-Simons term is generated in the three-dimensional electrodynamics. Under the same procedure, the Chern-Simons term is shown to be cancelled in the Maxwell-Chern-Simons theory for the appropriate value of the noncommutativity parameter. Hence the mutual interchange between Maxwell-Chern-Simons theory and pure Maxwell theory turns out to be generated within this method.Comment: Comments 5 pages, epl, version accepted for publication in Europhysics Letter

    Avaliacao de cultivares de mandioca em tres ecossistemas do Estado do Piaui.

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    Avaliando o potencial genetico de cultivares de mandioca no Piaui, foram conduzidos tres ensaios nos municipios de Eliseu Martins, Flores doPiaui e Regeneracao-PI, no ano agricola 1985/86. Foram quatro cultivares procedentes do Piaui (Vermelhinha, Joao Vaz Preto, Cruvela e EnganaLadrao) e em cada local foi adicionada um cultivar procedente do Centro Nacional de Pesquisa de Mandioca e Fruticultura-CNPMF, Cruz das Almas-BA (Aipim Bahia, Tola 6301 e Mamao). O delineamento estatistico utilizado foi o de blocos ao acaso com quatro repeticoes e cinco tratamentos constituidos pelas cultivares de mandioca. As cultivares Aimpim Bahia, Mamao e Tola 6301 apresentaram os maiores rendimentos de raizes frescas (34,17 t, 19,98 t e 16,71 t/ha) em Eliseu Martins, Regeneracao
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