405,778 research outputs found

    Dimensional Reduction via Noncommutative Spacetime: Bootstrap and Holography

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    Unlike noncommutative space, when space and time are noncommutative, it seems necessary to modify the usual scheme of quantum mechanics. We propose in this paper a simple generalization of the time evolution equation in quantum mechanics to incorporate the feature of a noncommutative spacetime. This equation is much more constraining than the usual Schr\"odinger equation in that the spatial dimension noncommuting with time is effectively reduced to a point in low energy. We thus call the new evolution equation the spacetime bootstrap equation, the dimensional reduction called for by this evolution seems close to what is required by the holographic principle. We will discuss several examples to demonstrate this point.Comment: 15 pages, harvmac. v2: typos corrected and some changes mad

    A geometric characterization of a sharp Hardy inequality

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    In this paper, we prove that the distance function of an open connected set in Rn+1\mathbb R^{n+1} with a C2C^{2} boundary is superharmonic in the distribution sense if and only if the boundary is {\em weakly mean convex}. We then prove that Hardy inequalities with a sharp constant hold on {weakly mean convex} C2C^{2} domains. Moreover, we show that the {weakly mean convexity} condition cannot be weakened. We also prove various improved Hardy inequalities on mean convex domains along the line of Brezis-Marcus \cite{BM}.Comment: The results were improved to C2C^2 domain

    Associated Charmonium Production in Low Energy p-pbar Annihilation

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    The QCD mechanisms underlying the exclusive strong decays and hadronic production amplitudes of charmonium remain poorly understood, despite decades of study and an increasingly detaled body of experimental information. One set of hadronic channels of special interest are those that include baryon-antibaryon states. These are being investigated experimentally at BES and CLEO-c in terms of their baryon resonance content, and are also of interest for the future PANDA experiment, in which charmonium and charmonium hybrids will be produced in p-pbar annihilation in association with light mesons. In this paper we develop a simple initial-state light meson emission model of the near-threshold associated charmonium production processes p pbar -> pi0 ccbar, and evaluate the differential and total cross sections for these reactions in this model. (Here we consider the ccbar states eta_c, J/psi, psi', chi_0 and chi_1.) The predicted near-threshold cross section for p pbar -> pi0 J/psi is found to be numerically similar to two previous theoretical estimates, and is roughly comparable to the (sparse) existing data for this process. The theoretical charmonium angular distributions predicted by this model are far from isotropic, which may be of interest for PANDA detector design studies.Comment: 6 pages, 4 figures, uses graphicx and feynm

    Rectifying "nanohomo" contacts of W-Ga-C composite pad and nanowire fabricated by focused-ion-beam induced chemical vapour deposition

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    We prepared W-Ga-C composite contacts on W-Ga-C composite nanowires by focused-ion-beam-induced chemical vapor deposition using a dual-beam scanning electron microscope/focused-ion-beam system. The current-voltage (I-V) characteristics of wires were found to change from nonlinear to linear with increasing wire thickness. For wires with small dimensions, which result in strong nonlinear I-V behavior at room temperature, pairs of contacts were fabricated along the wire under different ion energies and scanning modes. Nonlinear and asymmetric rectifying I-V characteristics were observed. The results suggest that nanoscaled W-Ga-C nanowires may behave similarly to semiconductors and that the contact characteristics may be modified using different deposition conditions. Furthermore, ohmiclike junctions could be formed through the use of specific deposition conditions for the contact pads and nanowires

    Revisiting the hot matter in the center of gamma-ray bursts and supernova

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    Hot matter with nucleons can be produced in the inner region of the neutrino-dominated accretion flow in gamma-ray bursts or during the proto-neutron star birth in successful supernova. The composition and equation of state of the matter depend on the dynamic β\beta equilibrium under various neutrino opacities. The strong interaction between nucleons may also play an important role. We plan to extend the previous studies by incorporating these two aspects in our model. The modification of the β\beta-equilibrium condition from neutrino optically thin to thick has been modeled by an equilibrium factor χ\chi ranging between the neutrino-freely-escaping case and the neutrino-trapped case. We employ the microscopic Brueckner-Hartree-Fock approach extended to the finite temperature regime to study the interacting nucleons. We show that the composition and chemical potentials of the hot nuclear matter for different densities and temperatures at each stage of β\beta equilibrium. We also compare our realistic equation of states with those of the free gas model. We find the neutrino opacity and the strong interaction between nucleons are important for the description and should be taken into account in model calculations.Comment: accepted Astronomy & Astrophysics (2013

    Study of Apollo water impact. Volume 1 - Hydrodynamic analysis of Apollo water impact Final report

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    Mathematical model for Apollo command module impact analysis on wate

    Measuring CP Violating Phases at a Future Linear Collider

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    At a future Linear Collider one will be able to determine the masses of charginos and neutralinos and their pair production cross sections to high accuracies. We show how systematically including the cross sections into the analysis improves the measurement of the underlying mass parameters, including potential CP violating phases. In addition, we investigate how experimental errors will affect the determination of these parameters. We present a first estimate on the lower limit of observable small phases and on the accuracy in determining large phases.Comment: 10 pages, 6 figures, RevTeX3.1, Version to be published in Physics Letters B, physics setup improved, figures added, conclusions unchange

    A self-learning particle swarm optimizer for global optimization problems

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    Copyright @ 2011 IEEE. All Rights Reserved. This article was made available through the Brunel Open Access Publishing Fund.Particle swarm optimization (PSO) has been shown as an effective tool for solving global optimization problems. So far, most PSO algorithms use a single learning pattern for all particles, which means that all particles in a swarm use the same strategy. This monotonic learning pattern may cause the lack of intelligence for a particular particle, which makes it unable to deal with different complex situations. This paper presents a novel algorithm, called self-learning particle swarm optimizer (SLPSO), for global optimization problems. In SLPSO, each particle has a set of four strategies to cope with different situations in the search space. The cooperation of the four strategies is implemented by an adaptive learning framework at the individual level, which can enable a particle to choose the optimal strategy according to its own local fitness landscape. The experimental study on a set of 45 test functions and two real-world problems show that SLPSO has a superior performance in comparison with several other peer algorithms.This work was supported by the Engineering and Physical Sciences Research Council of U.K. under Grants EP/E060722/1 and EP/E060722/2
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