306,005 research outputs found

    Solar cycle variations of the solar wind

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    Throughout the course of the past one and a half solar cycles, solar wind parameters measured near the ecliptic plane at 1 AU varied in the following way: speed and proton temperature have maxima during the declining phase and minima at solar minimum and are approximately anti-correlated with number density and electron temperature, while magnetic field magnitude and relative abundance of helium roughly follow the sunspot cycle. These variations are described in terms of the solar cycle variations of coronal holes, streamers, and transients. The solar wind signatures of the three features are discussed in turn, with special emphasis on the signature of transients, which is still in the process of being defined. It is proposed that magnetic clouds be identified with helium abundance enhancements and that they form the head of a transient surrounded by streamer like plasma, with an optional shock front. It is stressed that relative values of a parameter through a solar cycle should be compared beginning with the declining phase, especially in the case of magnetic field magnitude

    Managing strategy through business process

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    The work presented in this paper, following an in depth review of literature, developed a set of requirements for a Dynamic Strategy Management Process. Having evaluated the existing strategy management frameworks, models, methodologies, tools and techniques, the research concluded that although all approaches reviewed collectively met all the requirements, individually none of the approaches fulfilled all of these requirements. To fulfil these dynamic strategy management process requirements, PROPHESY (Process Oriented Performance Headed Strategy) was developed. The paper describes in some detail, the evaluation of the PROPHESY process and demonstrates its application through a case study. The paper concludes that strategy should focus on creating value that is independent for each business unit. This means developing horizontal strategies that have objectives of co-ordinating business processes and developing objectives that encourage the sharing of resources and skills

    Confinement and Mass Gap in Abelian Gauge

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    First, we present a simple confining abelian pure gauge theory. Classically, its kinetic term is not positive definite, and it contains a simple UV regularized F^4 interaction. This provoques the formation of a condensate ~ F^2 such that, at the saddle point of the effective potential, the wave function normalization constant of the abelian gauge fields vanishes exactly. Then we study SU(2) pure Yang-Mills theory in an abelian gauge and introduce an additional auxiliary field for a BRST invariant condensate of dimension 2, which renders the charged sector massive. Under simple assumptions its effective low energy theory reduces to the confining abelian model discussed before, and the vev of rho is seen to scale correctly with the renormalization point. Under these assumptions, the confinement condition Z_eff = 0 also holds for the massive charged sector, which suppresses the couplings of the charged fields to the abelian gauge bosons in the infrared regime.Comment: Explanations added, to appear in Eur. Phys. J.

    Confinement with Kalb - Ramond Fields

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    We consider models with N U(1) gauge fields A_{\mu}^n, N Kalb-Ramond fields B_{\mu \nu}^n, an arbitrary bare action and a fixed UV cutoff \Lambda. Under mild assumptions these can be obtained as effective low energy theories of SU(N+1) Yang Mills theories in the maximal abelian gauge. For a large class of bare actions they can be solved in the large N limit and exhibit confinement. The confining phase is characterized by an approximate ``low energy'' vector gauge symmetry under which the Kalb-Ramond fields B_{\mu\nu}^n transform. The same symmetry allows for a duality transformation showing that magnetic monopoles have condensed. The models allow for various mechanisms of confinement, depending on which sources for A_{\mu}^n or B_{\mu \nu}^n are switched on, but the area law for the Wilson loop is obtained in any case.Comment: corrected misprints and reference

    Performance of one-body reduced density matrix functionals for the homogeneous electron gas

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    The subject of this study is the exchange-correlation-energy functional of reduced density matrix functional theory. Approximations of this functional are tested by applying them to the homogeneous electron gas. We find that two approximations recently proposed by Gritsenko, Pernal, and Baerends, J. Chem. Phys., {\bf 122}, 204102 (2005), yield considerably better correlation energies and momentum distributions than previously known functionals. We introduce modifications to these functionals which, by construction, reproduce the exact correlation energy of the homogeneous electron gas
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