48,148 research outputs found

    Warped Tori with Almost Non-Negative Scalar Curvature

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    For sequences of warped product metrics on a 33-torus satisfying the scalar curvature bound Rj1jR_j \geq -\frac{1}{j}, uniform upper volume and diameter bounds, and a uniform lower area bound on the smallest minimal surface, we find a subsequence which converges in both the Gromov-Hausdorff and the Sormani-Wenger Intrinsic Flat sense to a flat 33-torus.Comment: 21 pages. The second version has no changes to the estimates, just a change in title and some exposition in response to a request by a senior mathematician. Minor revisions made suggested by the referee in version three. To appear in Geometriae Dedicat

    High Fidelity State Transfer Over an Unmodulated Linear XY Spin Chain

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    We provide a class of initial encodings that can be sent with a high fidelity over an unmodulated, linear, XY spin chain. As an example, an average fidelity of ninety-six percent can be obtained using an eleven-spin encoding to transmit a state over a chain containing ten-thousand spins. An analysis of the magnetic field dependence is given, and conditions for field optimization are provided.Comment: Replaced with published version. 8 pages, 5 figure

    Electron-Phonon Interaction in NbB_2 : A Comparison with MgB_2

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    We present a comparison of electron-phonon interaction in NbB_2 and MgB_2, calculated using full-potential, density-functional-based methods in P6/mmm crystal structure. Our results, described in terms of (i) electronic structure, (ii) phonon density of states F(\omega), (iii) Eliashberg function \alpha ^2F(\omega), and (iv) the solutions of the isotropic Eliashberg gap equation, clearly show significant differences in the electron-phonon interaction in NbB_2 and MgB_2. We find that the average electron-phonon coupling constant \lambda is equal to 0.59 for MgB_2 and 0.43 for NbB_2, leading to superconducting transition temperature T_c of around 22 K for MgB_2 and 3 K for NbB_2

    Integrating static and dynamic information for routing traffic

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    The efficiency of traffic routing on complex networks can be reflected by two key measurements i.e. the system capacity and the average data packets travel time. In this paper, we propose a mixing routing strategy by integrating local static and dynamic information for enhancing the efficiency of traffic on scale-free networks. The strategy is governed by a single parameter. Simulation results show that there exists a optimal parameter value by considering both maximizing the network capacity and reducing the packet travel time. Comparing with the strategy by adopting exclusive local static information, the new strategy shows its advantages in improving the efficiency of the system. The detailed analysis of the mixing strategy is provided. This work suggests that how to effectively utilize the larger degree nodes plays the key role in the scale-free traffic systems.Comment: 5 pages, 5 figure

    Sharing a common origin between the rotational and linear doppler effects

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    The well-known linear Doppler effect arises from the linear motion between source and observer, while the less well-known rotational Doppler effect arises from the rotational motion. Here, we present both theories and experiments illustrating the relationship between the rotational and linear Doppler effects. A spiral phaseplate is used to generate a light beam carrying orbital angular momentum and the frequency shift is measured arising from its rotational and/or linear motion. By considering either the motion-induced time-evolving phase or the momentum and energy conservation in light-matter interactions, we derive the rotational Doppler shift, linear Doppler shift, and overall Doppler shift associated with rotational and linear motions. We demonstrate the relationship between rotational and linear Doppler shifts, either of which can be derived from the other effect, thereby illustrating their shared origin. Moreover, the close relationship between rotational and linear Doppler effects is also deduced for a more general moving rough surface

    Proposal of Quantum Simulation of Pairing Model on an NMR Quantum Computer

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    We give out a proposal of quantum simulation of pairing model on an NMR quantum computer. In our proposal, we choose an appropriate initial state which can be easily prepared in experiment. Making use of feature of NMR measure and the technology of the second (discrete) Fourier transformation, our theoretical scheme can obtain the spectrum of paring model in principle. We concretely discuss the case in the concerned subspaces of pairing model and then, as an example, give out a simple initial state to get the gap of two the lowest energy levels in the given subspace. The quantum simulation to get more differences of energy levels is able to be discussed similarly.Comment: 5 pages, no figures, introducing and conclusion paragraphes are revise
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