43,761 research outputs found

    On the blow-up structure for the generalized periodic Camassa-Holm and Degasperis-Procesi equations

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    Considered herein are the generalized Camassa-Holm and Degasperis-Procesi equations in the spatially periodic setting. The precise blow-up scenarios of strong solutions are derived for both of equations. Several conditions on the initial data guaranteeing the development of singularities in finite time for strong solutions of these two equations are established. The exact blow-up rates are also determined. Finally, geometric descriptions of these two integrable equations from non-stretching invariant curve flows in centro-equiaffine geometries, pseudo-spherical surfaces and affine surfaces are given.Comment: 26 page

    Quantum secure direct communication based on supervised teleportation

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    We present a quantum secure direct communication(QSDC) scheme as an extension for a proposed supervised secure entanglement sharing protocol. Starting with a quick review on the supervised entanglement sharing protocol -- the "Wuhan" protocol [Y. Li and Y. Liu, arXiv:0709.1449v2], we primarily focus on its further extend using for a QSDC task, in which the communication attendant Alice encodes the secret message directly onto a sequence of 2-level particles which then can be faithfully teleported to Bob using the shared maximal entanglement states obtained by the previous "Wuhan" protocol. We also evaluate the security of the QSDC scheme, where an individual self-attack performed by Alice and Bob -- the out of control attack(OCA) is introduced and the robustness of our scheme on the OCA is documented.Comment: 5 pages, 1 table, oral contribution in the Conference on Quantum Optics and Applications in Computing and Communications, Photonics Asia 2007, Proc. of SPI

    Light speed variation from gamma ray bursts: criteria for low energy photons

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    We examine a method to detect the light speed variation from gamma ray burst data observed by the Fermi Gamma-ray Space Telescope (FGST). We suggest new criteria to determine the characteristic time for low energy photons by the energy curve and the average energy curve, and obtain similar results compared with those from the light curve. We offer a new criterion with both the light curve and the average energy curve to determine the characteristic time for low energy photons. We then apply the new criteria to the GBM NaI data, the GBM BGO data, and the LAT LLE data, and obtain consistent results for three different sets of low energy photons from different FERMI detectors.Comment: 26 latex pages, 23 figures, final version for publicatio