9,253 research outputs found

    A Cellular, Language Directed Computer Architecture

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    If a VLSI computer architecture is to influence the field of computing in some major way, it must have attractive properties in all important aspects affecting the design, production, and the use of the resulting computers. A computer architecture that is believed to have such properties is briefly discussed

    Soluble field theory with a massless gauge invariant limit

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    It is shown that there exists a soluble four parameter model in (1+1) dimensions all of whose propagators can be determined in terms of the corresponding known propagators of the vector coupling theory. Unlike the latter case, however, the limit of zero bare mass is nonsingular and yields a nontrivial theory with a rigorously unbroken gauge invariance.Comment: 7 pages, revtex, no figure

    Unification of the Soluble Two-dimensional vector coupling models

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    The general theory of a massless fermion coupled to a massive vector meson in two dimensions is formulated and solved to obtain the complete set of Green's functions. Both vector and axial vector couplings are included. In addition to the boson mass and the two coupling constants, a coefficient which denotes a particular current definition is required for a unique specification of the model. The resulting four parameter theory and its solution are shown to reduce in appropriate limits to all the known soluble models, including in particular the Schwinger model and its axial vector variant.Comment: 10 page

    Gamow shell-model calculations of drip-line oxygen isotopes

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    We employ the Gamow shell model (GSM) to describe low-lying states of the oxygen isotopes 24O and 25O. The many-body Schrodinger equation is solved starting from a two-body Hamiltonian defined by a renormalized low-momentum nucleon-nucleon (NN) interaction, and a spherical Berggren basis. The Berggren basis treats bound, resonant, and continuum states on an equal footing, and is therefore an appropriate representation of loosely bound and unbound nuclear states near threshold. We show that such a basis is necessary in order to obtain a detailed and correct description of the low-lying 1+ and 2+ excited states in 24O. On the other hand, we find that a correct description of binding energy systematics of the ground states is driven by proper treatment and inclusion of many-body correlation effects. This is supported by the fact that we get 25O unstable with respect to 24O in both oscillator and Berggren representations starting from a 22O core. Furthermore, we show that the structure of these loosely bound or unbound isotopes are strongly influenced by the 1S0 component of the NN interaction. This has important consequences for our understanding of nuclear stability.Comment: 5 pages, 3 figure

    Effective Interaction Techniques for the Gamow Shell Model

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    We apply a contour deformation technique in momentum space to the newly developed Gamow shell model, and study the drip-line nuclei 5He, 6He and 7He. A major problem in Gamow shell-model studies of nuclear many-body systems is the increasing dimensionality of many-body configurations due to the large number of resonant and complex continuum states necessary to reproduce bound and resonant state energies. We address this problem using two different effective operator approaches generalized to the complex momentum plane. These are the Lee-Suzuki similarity transformation method for complex interactions and the multi-reference perturbation theory method. The combination of these two approaches results in a large truncation of the relevant configurations compared with direct diagonalization. This offers interesting perspectives for studies of weakly bound systems.Comment: 18 pages, 17 figs, Revtex

    KASPAR in the wild - Initial findings from a pilot study

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    This extended abstract describes the initial pilot work when evaluating the use of the UH Humanoid Robot KASPAR in a specialist nursery for children with social and communication disorders. Staff and volunteers at the nursery were trained in the use of KASPAR and are currently using KASPAR in their day to day activities in the nursery. This paper focuses on the design and results from the initial interviews with the participants. Results high-light the challenges of transferring experimental technologies like KASPAR from a research setting into everyday practice

    Investigations of the lower and middle atmosphere at the Arecibo Observatory and a description of the new VHF radar project

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    The atmospheric science research at the Arecibo Observatory is performed by means of (active) radar methods and (passive) optical methods. The active methods utilize the 430 NHz radar, the S-band radar on 2380 MHz, and a recently constructed Very High Frequency (VHF) radar. The passive methods include measurements of the mesopause temperature by observing the rotational emissions from OH-bands. The VHF radar design is discussed
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