19,292 research outputs found

    Two-Site Quantum Random Walk

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    We study the measure theory of a two-site quantum random walk. The truncated decoherence functional defines a quantum measure ÎŒn\mu_n on the space of nn-paths, and the ÎŒn\mu_n in turn induce a quantum measure ÎŒ\mu on the cylinder sets within the space Ω\Omega of untruncated paths. Although ÎŒ\mu cannot be extended to a continuous quantum measure on the full σ\sigma-algebra generated by the cylinder sets, an important question is whether it can be extended to sufficiently many physically relevant subsets of Ω\Omega in a systematic way. We begin an investigation of this problem by showing that ÎŒ\mu can be extended to a quantum measure on a "quadratic algebra" of subsets of Ω\Omega that properly contains the cylinder sets. We also present a new characterization of the quantum integral on the nn-path space.Comment: 28 page

    The Pawns of War: A Personal Account of the Attack on VerrĂšres Ridge by The South Saskatchewan Regiment, 20 July 1944

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    A number of current books deal with Operations Goodwood and Atlantic, but scant attention has been paid to the 6th Canadian Infantry Brigade and its three regiments, the Queen’s Own Cameron Highlanders of Canada (CAM), the Fusiliers Mont-Royal (FMR) and the South Saskatchewan Regiment (SSR), and to the Essex Scottish Regiment which was attached to 6th Brigade during this operation. When our role has been discussed at all, historians have inferred that the SSR fled or withdrew in panic in this action. My role was as Commander “B” Company of the SSR, and later as Acting Commanding Officer (A/CO) of the SSR during this operation. I wish to record my memories of the battle supplemented by historical documentation which I hope will cause historians to review the 6th Brigade action of 20 July 1944

    Orthogonal frequency-division multiplexing in wireless communication systems with multimode fiber feeds

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    The feasibility of using multimode fiber as an inexpensive cell feed in broad-band indoor picocellular systems is investigated in this paper. The performance of coded orthogonal frequency-division multiplexing (OFDM) for a variety of multimode fiber profiles, including stepped index and -profile graded index fibers, is assessed. In addition to its ability to perform well in a frequency- selective multipath environment, OFDM is shown to offer good protection against the frequency selectivity of a dispersive multimode fiber. Data rates in excess of 100 Mb/s (without equalization) over a multimode fiber channel are possible, whereas they may be limited to some 20–30 Mb/s using conventional ASK modulation

    Characteristic Angles in the Wetting of an Angular Region: Deposit Growth

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    As was shown in an earlier paper [1], solids dispersed in a drying drop migrate to the (pinned) contact line. This migration is caused by outward flows driven by the loss of the solvent due to evaporation and by geometrical constraint that the drop maintains an equilibrium surface shape with a fixed boundary. Here, in continuation of our earlier paper [2], we theoretically investigate the evaporation rate, the flow field and the rate of growth of the deposit patterns in a drop over an angular sector on a plane substrate. Asymptotic power laws near the vertex (as distance to the vertex goes to zero) are obtained. A hydrodynamic model of fluid flow near the singularity of the vertex is developed and the velocity field is obtained. The rate of the deposit growth near the contact line is found in two time regimes. The deposited mass falls off as a weak power Gamma of distance close to the vertex and as a stronger power Beta of distance further from the vertex. The power Gamma depends only slightly on the opening angle Alpha and stays between roughly -1/3 and 0. The power Beta varies from -1 to 0 as the opening angle increases from 0 to 180 degrees. At a given distance from the vertex, the deposited mass grows faster and faster with time, with the greatest increase in the growth rate occurring at the early stages of the drying process.Comment: v1: 36 pages, 21 figures, LaTeX; submitted to Physical Review E; v2: minor additions to Abstract and Introductio

    A State Space Framework for Automatic Forecasting Using Exponential Smoothing Methods.

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    We provide a new approach to automatic business forecasting based on an extended range of exponential smoothing methods. Each method in our taxonomy of exponential smoothing methods can be shown to be equivalent to the forecasts obtained from a state space model. This allows (1) the easy calculation of the likelihood, the AIC and other model selection criteria; (2) the computation of prediction intervals for each method; and (3) random simulation from the underlying state space model. We demonstrate the methods by applying them to the data from the M-competition on the M3-competition.Automatic forecasting, exponential smoothing, prediction intervals, state space models.

    Aspects of Axion Phenomenology in a slice of AdS_5

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    Motivated by multi-throat considerations, we study the phenomenological implications of a bulk axion in a slice of AdS_5 with a large extra dimension: k~0.01 eV, kR > 1. In particular, we compare axion physics with a warped geometry to axions in flat compactifications. As in flat compactification scenarios, we find that the mass of the axion can become independent from the underlying Peccei-Quinn scale. Surprisingly, we find that in warped extra dimensions the axion's invisibility, cosmological viability, and basic phenomenology remain essentially unaltered in comparison to axions in flat compactifications.Comment: 25 pages, 9 figure

    Minimal speed of fronts of reaction-convection-diffusion equations

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    We study the minimal speed of propagating fronts of convection reaction diffusion equations of the form ut+Όϕ(u)ux=uxx+f(u)u_t + \mu \phi(u) u_x = u_{xx} +f(u) for positive reaction terms with fâ€Č(0>0f'(0 >0. The function ϕ(u)\phi(u) is continuous and vanishes at u=0u=0. A variational principle for the minimal speed of the waves is constructed from which upper and lower bounds are obtained. This permits the a priori assesment of the effect of the convective term on the minimal speed of the traveling fronts. If the convective term is not strong enough, it produces no effect on the minimal speed of the fronts. We show that if fâ€Čâ€Č(u)/fâ€Č(0)+Όϕâ€Č(u)<0f''(u)/\sqrt{f'(0)} + \mu \phi'(u) < 0, then the minimal speed is given by the linear value 2fâ€Č(0)2 \sqrt{f'(0)}, and the convective term has no effect on the minimal speed. The results are illustrated by applying them to the exactly solvable case ut+ÎŒuux=uxx+u(1−u)u_t + \mu u u_x = u_{xx} + u (1 -u). Results are also given for the density dependent diffusion case ut+Όϕ(u)ux=(D(u)ux)x+f(u)u_t + \mu \phi(u) u_x = (D(u)u_x)_x +f(u).Comment: revised, new results adde

    Axion-photon Couplings in Invisible Axion Models

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    We reexamine the axion-photon couplings in various invisible axion models motivated by the recent proposal of using optical interferometry at the ASST facility in the SSCL to search for axion. We illustrate that the assignment of U(1)PQU(1)_{PQ} charges for the fermion fields plays an important role in determining the couplings. Several simple non-minimal invisible axion models with suppressed and enhanced axion-photon couplings are constructed, respectively. We also discuss the implications of possible new experiments to detect solar axions by conversion to XX-rays in a static magnetic apparatus tracking the sun.Comment: 14 pages, LaTeX fil

    Studies of Mass and Size Effects in Three-Dimensional Vibrofluidized Granular Mixtures

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    We examine the steady state properties of binary systems of driven inelastic hard spheres. The spheres, which move under the influence of gravity, are contained in a vertical cylinder with a vibrating base. We computed the trajectories of the spheres using an event-driven molecular dynamics algorithm. In the first part of the study, we chose simulation parameters that match those of experiments performed by Wildman and Parker. Various properties computed from the simulation including the density profile, granular temperature and circulation pattern are in good qualitative agreement with the experiments. We then studied the effect of varying the mass ratio and the size ratio independently while holding the other parameters constant. The mass and size ratio are shown to affect the distribution of the energy. The changes in the energy distributions affect the packing fraction and temperature of each component. The temperature of the heavier component has a non-linear dependence on the mass of the lighter component, while the temperature of the lighter component is approximately proportional to its mass. The temperature of both components is inversely dependent on the size of the smaller component.Comment: 14 Pages, 12 Figures, RevTeX

    State estimation for large ensembles

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