132,720 research outputs found

    Current collection in an anisotropic plasma

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    A general method is given to derive the current-potential relations in anisotropic plasmas. Orbit limit current is assumed. The collector is a conductive sphere or an infinite cylinder. Any distribution which is an arbitrary function of the velocity vector can be considered as a superposition of many mono-energetic beams whose current-potential relations are known. The results for two typical pitch angle distributions are derived and discussed in detail. The general properties of the current potential relations are very similar to that of a Maxwellian plasma except for an effective temperature which varies with the angle between the magnetic field and the charging surface. The conclusions are meaningful to generalized geometries

    Partial Differential Chow Forms and a Type of Partial Differential Chow varieties

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    We first present an intersection theory of partial differential varieties with quasi-generic differential hypersurfaces. Then based on the generic intersection theory, we define the partial differential Chow form for an irreducible partial differential variety VV of Kolchin polynomial Ο‰V(t)=(d+1)(t+mm)βˆ’(t+mβˆ’sm)\omega_V(t)=(d+1){t+m\choose m}-{t+m-s\choose m}. And we establish for the partial differential Chow form most of the basic properties of the ordinary differential Chow form. Furthermore, we prove the existence of a type of partial differential Chow varieties.Comment: 30 page

    Observation of a "Ridge" correlation structure in high multiplicity proton-proton collisions: A brief review

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    This paper briefly reviews the striking experimental observation of a ridge-like dihadron correlation structure in high multiplicity proton-proton collisions at the Large Hadron Collider (LHC). Recent progress of both experimental and theoretical efforts on understanding the physical origin of the novel effect is reviewed. Outlook on future direction of possible new studies is discussed.Comment: 16 pages, 12 figures, brief review for Modern Physics Letter

    System size dependence of two-particle angular correlations in p+p, Cu+Cu and Au+Au collisions

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    We present a systematic study of two-particle angular correlations in p+p, Cu+Cu and Au+Au collisions over a broad range of pseudorapidity and azimuthal angle. The PHOBOS detector has a uniquely large angular coverage for inclusive charged particles, which allows for the study of correlations on both long- and short-range scales. A complex two-dimensional correlation structure emerges which is interpreted in the context of a cluster model. The cluster size and its decay width are extracted from the two-particle pseudorapidity correlation function. The cluster size found in semi-central Cu+Cu and Au+Au collisions is comparable to that found in p+p but a non-trivial increase of cluster size with decreasing centrality is observed. Moreover, the comparison between Cu+Cu and Au+Au systems shows an interesting scaling of the cluster size with the measured fraction of total cross section (which is related to b/2Rb/2R), suggesting a geometric origin. These results should provide insight into the hadronization stage of the hot and dense medium created in heavy ion collisions.Comment: 4 pages, 5 figures, presented at the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur, India, February 4-10, 200

    Two point extremal Gromov-Witten invariants of Hilbert schemes of points on surfaces

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    Given an algebraic surface XX, the Hilbert scheme X[n]X^{[n]} of nn-points on XX admits a contraction morphism to the nn-fold symmetric product X(n)X^{(n)} with the extremal ray generated by a class Ξ²n\beta_n of a rational curve. We determine the two point extremal GW-invariants of X[n]X^{[n]} with respect to the class dΞ²nd\beta_n for a simply-connected projective surface XX and the quantum first Chern class operator of the tautological bundle on X[n]X^{[n]}. The methods used are vertex algebraic description of Hβˆ—(X[n])H^*(X^{[n]}), the localization technique applied to X=P2X=\mathbb P^2, and a generalization of the reduction theorem of Kiem-J. Li to the case of meromorphic 2-forms

    Comment on "Cosmological Topological Massive Gravitons and Photons"

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    In a recent paper (arXiv: 0801.4566) it was shown that all global energy eigenstates of asymptotically AdS3AdS_3 chiral gravity have non-negative energy at the linearized level. This result was questioned (arXiv: 0803.3998) by Carlip, Deser, Waldron and Wise (CDWW), who work on the Poincare patch. They exhibit a linearized solution of chiral gravity and claim that it has negative energy and is smooth at the boundary. We show that the solution of CDWW is smooth only on that part of the boundary of AdS3AdS_3 included in the Poincare patch. Extended to global AdS3AdS_3, it is divergent at the boundary point not included in the Poincare patch. Hence it is consistent with the results of (arXiv: 0801.4566).Comment: 4 pages, comment on arXiv 0803.3998 [hep-th

    Quantum differential cryptanalysis to the block ciphers

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    Differential cryptanalysis is one of the most popular methods in attacking block ciphers. However, there still some limitations in traditional differential cryptanalysis. On the other hand, researches of quantum algorithms have made great progress nowadays. This paper proposes two methods to apply quantum algorithms in differential cryptanalysis, and analysis their efficiencies and success probabilities. One method is using quantum algorithm in the high probability differential finding period for every S-Box. The second method is taking the encryption as a whole, using quantum algorithm in this process.Comment: 11 pages, no figure

    Synchronized output regulation of nonlinear multi-agent systems

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    This paper considers the synchronized output regulation (SOR) problem of nonlinear multi-agent systems with switching graph. The SOR means that all agents regulate their outputs to synchronize on the output of a predefined common exosystem. Each agent constructs its local exosystem with the same dynamics as that of the common exosystem and exchanges the state information of the local exosystem. It is shown that the SOR is solvable under the assumptions same as that for nonlinear output regulation of a single agent, if the switching graph satisfies the bounded interconnectivity times condition. Both state feedback and output feedback are addressed. A numerical simulation is made to show the efficacy of the analytic results.Comment: 20 pages, 2 figures, submitted to International Journal of Contro

    Contragredient representations over local fields of positive characteristic

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    It is conjectured by Adams-Vogan and Prasad that under the local Langlands correspondence, the L-parameter of the contragredient representation equals that of the original representation composed with the Chevalley involution of the L-group. We verify a variant of their prediction for all connected reductive groups over local fields of positive characteristic, in terms of the local Langlands parameterization of Genestier-Lafforgue. We deduce this from a global result for cuspidal automorphic representations over function fields, which is in turn based on a description of the transposes of V. Lafforgue's excursion operators.Comment: 42 pages. Updated the reference

    Dynamical transitions in a modulated Landau-Zener model with finite driving fields

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    We investigate a special time-dependent quantum model which assumes the Landau-Zener driving form but with an overall modulation of the intensity of the pulsing field. We demonstrate that the dynamics of the system, including the two-level case as well as its multi-level extension, is exactly solvable analytically. Differing from the original Landau-Zener model, the nonadiabatic effect of the evolution in the present driving process does not destroy the desired population transfer. As the sweep protocol employs only the finite driving fields which tend to zero asymptotically, the cutoff error due to the truncation of the driving pulse to the finite time interval turns out to be negligibly small. Furthermore, we investigate the noise effect on the driving protocol due to the dissipation of the surrounding environment. The losses of the fidelity in the protocol caused by both the phase damping process and the random spin flip noise are estimated by solving numerically the corresponding master equations within the Markovian regime.Comment: 6 pages, 4 figure
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