619 research outputs found

    Investigation of the spectra of coupled polaritons on the periodically modulated metallic layer and the narrow regions of anomalous transparency

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    The paper deals with the theoretical investigation of plane, normally incident electromagnetic wave transmission through the flat metal film whose dielectric constant has small periodical sinusoidal modulation in one dimension parallel to the projection of the electric field onto the film surface. The dependencies of the film transmittancy on the parameters of the problem (frequency, modulation depth and absorption) are examined. It is shown that the film transmittancy increases considerably when the conditions for resonance interaction of an incident electromagnetic wave with surface plasmon polaritons (SPPs) are met. It is found that for small but finite absorption there are two frequencies in the vicinity of which the transmittancy can achieve the values of the order of unity due to resonances on symmetric and antisymmetric (relative to the mean plane) SPP modes. It is shown that for each value of absorption there exists a certain optimal modulation depth, which maximizes the resonance transparency.Comment: 18 pages, 8 figures, proceeding of conference "Plasmonics: metallic nanostructures and their optical properties", SPIE's 48-th Annual Meeting, 3-8 August, 2003, San Diego, US

    Tectonics and volcanisms of Mars

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    Televised images of Mars transmitted from interplanetary stations are used to develop a theory of the structure and development of the planet. Crater chronology, the structure of planetary bodies in the Earth group, and a comparison of the Earth planetary bodies are among the factors included

    Modeling of Return on Pension Funds, Taking into Well-being of Older Generation

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    The hypothesis that the well-being of the older generation can be improved by increasing the efficiency of pension savings investments into more profitable securities is proposed.A key factor, which increases the return on investment at a constant level of risk, is to diversify risk in the preparation of the portfolio. The well-being of older generations in terms of the need for optimum use of pension savings is considered. Four types of securities with different levels of risk and return, which theoretically can be invested pension funds are taken for analysis. Opportunities for investment securities in the simple and expanded portfolios are determined on the basis of existing legislation. Portfolios with different risk levels are compared. The principle of diversification is used. The curve of return and risk of various possible investment portfolios is simulated. The study is based on statistical methods.The opportunities for investing pension savings in securities with a higher level of profitability while maintaining a constant risk is demonstrated. The study focused on the revision of legislation in the field of investments of the pension funds of the Russian Federation in the stocks and bonds of Russian companies

    Erratum to: Resonances from QCD bound states and the 750 GeV diphoton excess

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    On Black Fundamental Strings

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    We study aspects of four dimensional black holes with two electric charges, corresponding to fundamental strings with generic momentum and winding on an internal circle. The perturbative \alpha' correction to such black holes and their gravitational thermodynamics is obtained.Comment: 17 pages, v2: published versio

    The String Landscape, Black Holes and Gravity as the Weakest Force

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    We conjecture a general upper bound on the strength of gravity relative to gauge forces in quantum gravity. This implies, in particular, that in a four-dimensional theory with gravity and a U(1) gauge field with gauge coupling g, there is a new ultraviolet scale Lambda=g M_{Pl}, invisible to the low-energy effective field theorist, which sets a cutoff on the validity of the effective theory. Moreover, there is some light charged particle with mass smaller than or equal to Lambda. The bound is motivated by arguments involving holography and absence of remnants, the (in) stability of black holes as well as the non-existence of global symmetries in string theory. A sharp form of the conjecture is that there are always light "elementary" electric and magnetic objects with a mass/charge ratio smaller than the corresponding ratio for macroscopic extremal black holes, allowing extremal black holes to decay. This conjecture is supported by a number of non-trivial examples in string theory. It implies the necessary presence of new physics beneath the Planck scale, not far from the GUT scale, and explains why some apparently natural models of inflation resist an embedding in string theory.Comment: 20 pages, LaTeX, 5 EPS figures; v2: minor correction

    Robustness of Sound Speed and Jet Quenching for Gauge/Gravity Models of Hot QCD

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    We probe the effectiveness and robustness of a simple gauge/gravity dual model of the QCD fireball that breaks conformal symmetry by constructing a family of similar geometries that solve the scalar/gravity equations of motion. This family has two parameters, one of which is associated to the temperature. We calculate two quantities, the speed of sound and the jet-quenching parameter. We find the speed of sound to be universal and robust over all the geometries when appropriate units are used, while the jet-quenching parameter varies significantly away from the conformal limit. We note that the overall structure of the jet-quenching depends strongly on whether the running scalar is the dilaton or not. We also discuss the variation of the scalar potential over our family of solutions, and truncate our results to where the associated error is small.Comment: 21 pages, 9 figures, LaTeX. v2:references added, minor correction to speed of sound; conclusions unchange

    Excitation of surface plasmon-polaritons in metal films with double periodic modulation: anomalous optical effects

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    We perform a thorough theoretical analysis of resonance effects when an arbitrarily polarized plane monochromatic wave is incident onto a double periodically modulated metal film sandwiched by two different transparent media. The proposed theory offers a generalization of the theory that had been build in our recent papers for the simplest case of one-dimensional structures to two-dimensional ones. A special emphasis is placed on the films with the modulation caused by cylindrical inclusions, hence, the results obtained are applicable to the films used in the experiments. We discuss a spectral composition of modulated films and highlight the principal role of ``resonance'' and ``coupling'' modulation harmonics. All the originating multiple resonances are examined in detail. The transformation coefficients corresponding to different diffraction orders are investigated in the vicinity of each resonance. We make a comparison between our theory and recent experiments concerning enhanced light transmittance and show the ways of increasing the efficiency of these phenomena. In the appendix we demonstrate a close analogy between ELT effect and peculiarities of a forced motion of two coupled classical oscillators.Comment: 24 pages, 17 figure

    Large Charge Four-Dimensional Extremal N=2 Black Holes with R^2-Terms

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    We consider N=2 supergravity in four dimensions with small R^2 curvature corrections. We construct large charge extremal supersymmetric and non-supersymmetric black hole solutions in all space, and analyze their thermodynamic properties.Comment: 18 pages. v2,3: minor fixe

    Shear viscosity, instability and the upper bound of the Gauss-Bonnet coupling constant

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    We compute the dimensionality dependence of η/s\eta/s for charged black branes with Gauss-Bonnet correction. We find that both causality and stability constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in the infinite dimensionality limit. We further show that higher dimensionality stabilize the gravitational perturbation. The stabilization of the perturbation in higher dimensional space-time is a straightforward consequence of the Gauss-Bonnet coupling constant bound.Comment: 16 pages,3 figures+3 tables,typos corrected, published versio
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