17,935 research outputs found

    On the anomalous mass defect of strange stars in the Field Correlator Method

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    We investigate general aspects of the mass defects of strange stars in the context of the Field Correlator Method, without magnetic field. The main parameters of the model that enter the corresponding nonperturbative equation of state of the quark gluon plasma are the gluon condensate G2G_2 and the large distance static QQˉQ{\bar Q} potential V1V_1. We calculate mass defects of stellar configurations in the central density range 11<logρc<1811<\log\rho_c<18. In general, the mass defects are strongly dependent on the model parameters. For a large range of values of G2G_2 and V1V_1, we obtain anomalous mass defects with magnitudes around 105310^{53}\,erg\,, of the same order of the observed energies of gamma-ray bursts and neutrino emissions in SN1987A, and of the theoretically predicted energies of the quark-novae explosions.Comment: 24 pages, 6 figure

    Low mass strange stars and the compact star 1E1207.4-5209 in the Field Correlator Method

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    We investigate the possible existence of anomalous mass defects in the low mass region of stellar sequences of strange stars. We employ the nonperturbative equation of state derived in the framework of the Field Correlator Method to describe the hydrostatic equilibrium of the strange matter. The large distance static QQˉQ{\bar Q} potential V1V_1 and the gluon condensate G2G_2 are the main parameters of the model. We use the surface gravitational redshift measurements as a probe to determine the ratio (P/E)C({\cal P}/{\cal E})_C at the center of strange stars. For V1=0V_1=0 and G_2\gappr0.035\,{\rm GeV}^4\,, we show that (P/E)C0.262({\cal P}/{\cal E})_C\simeq0.262 and the corresponding redshift zS0.47z_S\simeq0.47 are limiting values, at the maximum mass of the highest mass stellar sequence. As a direct application of our study, we try to determine the values of V1V_1 and G2G_2 from astrophysical observations of the compact star 1E\,1207.4-5209. Due to the uncertainties in the surface redshift determination, we made two attempts to obtain the model parameters. Our findings show that (P/E)C=0.073+0.024+0.029({\cal P}/{\cal E})_C=0.073^{+0.029}_{+0.024}\, at 68\% confidence, V1=0.44±0.10V_1=0.44\pm0.10\,GeV at 90\% confidence and G2=0.008±0.001GeV4G_2=0.008\pm0.001\,{\rm GeV}^4 at 95\% confidence \, in the first attempt; and (P/E)C=0.073+0.024+0.029=0.087±0.028({\cal P}/{\cal E})_C=0.073^{+0.029}_{+0.024}=0.087\pm0.028\, at 71\% confidence, V1=0.43±0.085V_1=0.43\pm0.085\,GeV at 94\% confidence and G2=0.0093±0.00092GeV4G_2=0.0093\pm0.00092\,{\rm GeV}^4 at 94\% confidence in the second attempt. These values of V1V_1 and G2G_2 are in reasonable agreement with the lattice and QCD sum rules calculations. As a consequence of the high values of V1V_1 and G2G_2, the anomalous mass defects of 1E\,1207.4-5209 are Δ2M2.56×1053|\Delta_2M|\simeq2.56\times10^{53}\,erg\, in the first attempt and Δ2M2.94×1053|\Delta_2M|\simeq2.94\times10^{53}\,erg\, in the second attempt.Comment: 34 pages, 15 figure

    Enhanced Optical Dichroism of Graphene Nanoribbons

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    The optical conductivity of graphene nanoribbons is analytical and exactly derived. It is shown that the absence of translation invariance along the transverse direction allows considerable intra-band absorption in a narrow frequency window that varies with the ribbon width, and lies in the THz range domain for ribbons 10-100nm wide. In this spectral region the absorption anisotropy can be as high as two orders of magnitude, which renders the medium strongly dichroic, and allows for a very high degree of polarization (up to ~85) with just a single layer of graphene. The effect is resilient to level broadening of the ribbon spectrum potentially induced by disorder. Using a cavity for impedance enhancement, or a stack of few layer nanoribbons, these values can reach almost 100%. This opens a potential prospect of employing graphene ribbon structures as efficient polarizers in the far IR and THz frequencies.Comment: Revised version. 10 pages, 7 figure

    New methodologies for the promotion of Geological Heritage using multimedia technology, 3D and augmented reality.

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    [Excerpt] The Internet and several hardware and software options that are currently available are very efficient ways for the promotion of geoparks, geoheritage and geosciences. The aim of this paper is to present a new and interactive way of gathering data into a website, based on several new web and photogrammetric technologies, applied to the Terras de Cavaleiros Global Geopark (Portugal). [...]info:eu-repo/semantics/publishedVersio

    Características do herbicida S-Metolachlor nas culturas de milho e sorgo.

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    bitstream/CNPMS/16188/1/Circ_36.pd

    Non universality of entanglement convertibility

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    Recently, it has been suggested that operational properties connected to quantum computation can be alternative indicators of quantum phase transitions. In this work we systematically study these operational properties in 1D systems that present phase transitions of different orders. For this purpose, we evaluate the local convertibility between bipartite ground states. Our results suggest that the operational properties, related to non-analyticities of the entanglement spectrum, are good detectors of explicit symmetries of the model, but not necessarily of phase transitions. We also show that thermodynamically equivalent phases, such as Luttinger liquids, may display different convertibility properties depending on the underlying microscopic model.Comment: 5 pages + references, 4 figures - improved versio

    Tolerância de hibridos de milho ao herbicida nicosulfuron.

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    Como objetivo de avaliar a tolerância dos híbridos de milho BRS 3060, 3101, 2114 e 2110 a doses crescentes do herbicida nicosulfuron. foi instalado um ensaio de campo na área experimental do Centro de Pesquisa da Embrapa Milho e Sorgo, município de Sete Lagoas-MG. durante o ano agrícola 1998/1999. A densidade de plantio foi de 50.000 plantas por hectare, e as doses do nicosulfuron foram de 50, 60 e 70 g ta. ha' -1, mais um tratamento testemunha que não recebeu aplicação do produto. mas que permaneceu limpo durante todo o ciclo da cultura. O delineamento experimental adotado foi em blocos ao acaso com três repetições, em esquema fatorial 4 x 4. A aplicação do produto foi realizada quando as plantas de milho se encontravam no estádio de quatro a seis folhas, ou seja, 20 dias após emergência das plantas. As avaliações de fitotoxicidade foram feitas aos 7, 14 e 21 dias após aplicação dos tratamentos herbicida. Somente o BRS 3060 permaneceu com efeito fitotóxico muito leve nas avaliações realizadas aos 14 e 21 dias após aplicação, sem comprometer o rendimento de grãos. Os resultados indicam que o herbicida nicosulfuron pode ser aplicado para o controle de plantas daninhas em híbridos de milho BRS 3060, 3101. 2114 e 2110 nas doses de 50 a 70 g ta. ha -1, sem causar danos significativos ao desenvolvimento e à produção da cultura
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