27,771 research outputs found

    Exact Solutions to Sourceless Charged Massive Scalar Field Equation on Kerr-Newman Background

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    The separated radial part of a sourceless massive complex scalar field equation on the Kerr-Newman black hole background is shown to be a generalized spin-weighted spheroidal wave equation of imaginary number order. While the separated angular part is an ordinary spheroidal wave equation. General exact solutions in integral forms and in power series expansion as well as several special solutions with physical interest are given for the radial equation in the non-extreme case. In the extreme case, power series solution to the radial equation is briefly studied. Recurrence relations between coefficients in power series expansion of general solutions and connection between the radial equation are discussed in both cases.Comment: 22 Pages, in LaTex, no figure, to appear in J. Math. Phy

    Scheme for sharing classical information via tripartite entangled states

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    We investigate schemes for quantum secret sharing and quantum dense coding via tripartite entangled states. We present a scheme for sharing classical information via entanglement swapping using two tripartite entangled GHZ states. In order to throw light upon the security affairs of the quantum dense coding protocol, we also suggest a secure quantum dense coding scheme via W state in analogy with the theory of sharing information among involved users.Comment: 4 pages, no figure. A complete rewrritten vession, accepted for publication in Chinese Physic

    Violence detection based on spatio-temporal feature and fisher vector

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    © Springer Nature Switzerland AG 2018. A novel framework based on local spatio-temporal features and a Bag-of-Words (BoW) model is proposed for violence detection. The framework utilizes Dense Trajectories (DT) and MPEG flow video descriptor (MF) as feature descriptors and employs Fisher Vector (FV) in feature coding. DT and MF algorithms are more descriptive and robust, because they are combinations of various feature descriptors, which describe trajectory shape, appearance, motion and motion boundary, respectively. FV is applied to transform low level features to high level features. FV method preserves much information, because not only the affiliations of descriptors are found in the codebook, but also the first and second order statistics are used to represent videos. Some tricks, that PCA, K-means++ and codebook size, are used to improve the final performance of video classification. In comprehensive consideration of accuracy, speed and application scenarios, the proposed method for violence detection is analysed. Experimental results show that the proposed approach outperforms the state-of-the-art approaches for violence detection in both crowd scenes and non-crowd scenes

    Massive Complex Scalar Field in a Kerr-Sen Black Hole Background: Exact Solution of Wave Equation and Hawking Radiation

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    The separated radial part of a massive complex scalar wave equation in the Kerr-Sen geometry is shown to satisfy the generalized spheroidal wave equation which is, in fact, a confluent Heun equation up to a multiplier. The Hawking evaporation of scalar particles in the Kerr-Sen black hole background is investigated by the Damour-Ruffini-Sannan's method. It is shown that quantum thermal effect of the Kerr-Sen black hole has the same characteras that of the Kerr-Newman black hole.Comment: Revtex, 5 pages, no figure, submitted to Phys. Rev.

    Nonorthogonal decoy-state Quantum Key Distribution

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    In practical quantum key distribution (QKD), weak coherent states as the photon sources have a limit in secure key rate and transmission distance because of the existence of multiphoton pulses and heavy loss in transmission line. Decoy states method and nonorthogonal encoding protocol are two important weapons to combat these effects. Here, we combine these two methods and propose a efficient method that can substantially improve the performance of QKD. We find a 79 km increase in transmission distance over the prior record using decoy states method.Comment: 4 pages, 1 figure; Revtex4, submitted to PR
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