A method for evaluating models that use galaxy rotation curves to derive the density profiles

There are some approaches, either based on General Relativity (GR) or modified gravity, that use galaxy rotation curves to derive the matter density of the corresponding galaxy, and this procedure would either indicate a partial or a complete elimination of dark matter in galaxies. Here we review these approaches, clarify the difficulties on this inverted procedure, present a method for evaluating them, and use it to test two specific approaches that are based on GR: the Cooperstock-Tieu (CT) and the Balasin-Grumiller (BG) approaches. Using this new method, we find that neither of the tested approaches can satisfactorily fit the observational data without dark matter. The CT approach results can be significantly improved if some dark matter is considered, while for the BG approach no usual dark matter halo can improve its results.Comment: 11 pages, 2 figures, 4 tables. v2: diverse text improvements, no changes in the conclusions. Version accepted in MNRA

Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics

In this work we show how to engineer bilinear and quadratic Hamiltonians in cavity quantum electrodynamics (QED) through the interaction of a single driven two-level atom with cavity modes. The validity of the engineered Hamiltonians is numerically analyzed even considering the effects of both dissipative mechanisms, the cavity field and the atom. The present scheme can be used, in both optical and microwave regimes, for quantum state preparation, the implementation of quantum logical operations, and fundamental tests of quantum theory.Comment: 11 pages, 3 figure

Nearest neighbor embedding with different time delays

A nearest neighbor based selection of time delays for phase space reconstruction is proposed and compared to the standard use of time delayed mutual information. The possibility of using different time delays for consecutive dimensions is considered. A case study of numerically generated solutions of the Lorenz system is used for illustration. The effect of contamination with various levels of additive Gaussian white noise is discussed.Comment: 4 pages, 5 figures, updated to final versio

Plantios comerciais de cupuaçuzeiro são fontes de novas cultivares?

A procura por novos materiais é uma prática incessante em qualquer programa de melhoramento genético. Os pomares de cupuaçuzeiro do município de Tomé Açu - Pará, por apresentarem alta variabilidade, oferecem oportunidade de que sejam selecionadas matrizes com boas características de produção de frutos. O objetivo desta pesquisa foi avaliar clones de cupuaçuzeiro oriundos de plantios comerciais, para identificar e selecionar matrizes interessantes para o programa de melhoramento genético da espécie. Dezoito matrizes foram, inicialmente, identificadas nos pomares comerciais, e depois clonadas. O experimento foi instalado a campo, em fevereiro/1999, no delineamento blocos inteiramente casualizados, com dez repetições, sendo uma planta por parcela. Foram coletados dados do número de frutos produzidos por planta, bem como, o peso do fruto, peso de sementes e polpa por fruto. Os dados revelaram boa variabilidade entre os clones no tocante ao número de frutos, entretanto, houve pouca variação para as características componentes do fruto. O clone 378 destacou-se como o material mais promissor para todas as variáveis estudadas. Quanto à produção de frutos também merece destaque o clone 366 e para produção de sementes o clone 375. Este clone também teve bom desempenho na produção de polpa, assim como os clones 366 e 415. Pelo comportamento apresentado neste ensaio, os clones 378, 375 e 366 deverão ser aproveitados pelo programa de melhoramento genético. Entretanto, necessitam ser testados numa escala experimental ampliada, antes da seleção final.PIBIC-2011

Nonadiabatic coherent evolution of two-level systems under spontaneous decay

In this paper we extend current perspectives in engineering reservoirs by producing a time-dependent master equation leading to a nonstationary superposition equilibrium state that can be nonadiabatically controlled by the system-reservoir parameters. Working with an ion trapped inside a nonindeal cavity we first engineer effective Hamiltonians that couple the electronic states of the ion with the cavity mode. Subsequently, two classes of decoherence-free evolution of the superposition of the ground and decaying excited levels are achieved: those with time-dependent azimuthal or polar angle. As an application, we generalise the purpose of an earlier study [Phys. Rev. Lett. 96, 150403 (2006)], showing how to observe the geometric phases acquired by the protected nonstationary states even under a nonadiabatic evolution.Comment: 5 pages, no figure