2,913 research outputs found

    A proof of the Gutzwiller Semiclassical Trace Formula using Coherent States Decomposition

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    The Gutzwiller semiclassical trace formula links the eigenvalues of the Scrodinger operator ^H with the closed orbits of the corresponding classical mechanical system, associated with the Hamiltonian H, when the Planck constant is small ("semiclassical regime"). Gutzwiller gave a heuristic proof, using the Feynman integral representation for the propagator of ^H. Later on mathematicians gave rigorous proofs of this trace formula, under different settings, using the theory of Fourier Integral Operators and Lagrangian manifolds. Here we want to show how the use of coherent states (or gaussian beams) allows us to give a simple and direct proof.Comment: 17 pages, LaTeX, available on http://qcd.th.u-psud.f

    The Virgo Alignment Puzzle in Propagation of Radiation on Cosmological Scales

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    We reconsider analysis of data on the cosmic microwave background on the largest angular scales. Temperature multipoles of any order factor naturally into a direct product of axial quantities and cosets. Striking coincidences exist among the axes associated with the dipole, quadrupole, and octupole CMB moments. These axes also coincide well with two other axes independently determined from polarizations at radio and optical frequencies propagating on cosmological scales. The five coincident axes indicate physical correlation and anisotropic properties of the cosmic medium not predicted by the conventional Big Bang scenario. We consider various mechanisms, including foreground corrections, as candidates for the observed correlations. We also consider whether the propagation anomalies may be a signal of ``dark energy'' in the form of a condensed background field. Perhaps {\it light propagation} will prove to be an effective way to look for the effects of {\it dark energy}.Comment: 24 pages, 4 figures, minor changes, no change in result or conclusions. to appear in IJMP

    Hadron Helicity Violation in Exclusive Processes: Quantitative Calculations in Leading Order QCD

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    We study a new mechanism for hadronic helicity flip in high energy hard exclusive reactions. The mechanism proceeds in the limit of perfect chiral symmetry, namely without any need to flip a quark helicity. The fundamental feature of the new mechanism is the breaking of rotational symmetry of the hard collision by a scattering plane in processes involving independent quark scattering. We show that in the impulse approximation there is no evidence for of the helicity violating process as the energy or momentum transfer Q2Q^2 is increased over the region 1 GeV^2 < Q^2 < 100 GeV^2. In the asymptotic region Q^2> 1000 GeV^2, a saddle point approximation with doubly logarithmic accuracy yields suppression by a fraction of power of Q^2. ``Chirally--odd" exclusive wave functions which carry non--zero orbital angular momentum and yet are leading order in the high energy limit, play an important role.Comment: uuencoded LaTeX file (21 pages) and PostScript figure

    Systematic Analysis Method for Color Transparency Experiments

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    We introduce a data analysis procedure for color transparency experiments which is considerably less model dependent than the transparency ratio method. The new method is based on fitting the shape of the A dependence of the nuclear cross section at fixed momentum transfer to determine the effective attenuation cross section for hadrons propagating through the nucleus. The procedure does not require assumptions about the hard scattering rate inside the nuclear medium. Instead, the hard scattering rate is deduced directly from the data. The only theoretical input necessary is in modelling the attenuation due to the nuclear medium, for which we use a simple exponential law. We apply this procedure to the Brookhaven experiment of Carroll et al and find that it clearly shows color transparency: the effective attenuation cross section in events with momentum transfer Q2Q^2 is approximately $40\ mb\ (2.2\ GeV^2/Q^2)$. The fit to the data also supports the idea that the hard scattering inside the nuclear medium is closer to perturbative QCD predictions than is the scattering of isolated protons in free space. We also discuss the application of our approach to electroproduction experiments.Comment: 11 pages, 11 figures (figures not included, available upon request), report # KU-HEP-92-2

    Logistics salience impact on logistics capabilities and performance

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    Purpose – The purpose of this manuscript is to assess the impact of logistics salience on logistics capabilities and performance. Specifically, the impact of logistics salience on logistics innovativeness and logistics service differentiation is measured along with logistics innovativeness and logistics service differentiation effect on logistics performance. Design/methodology/approach – Conclusions were drawn from survey data gathered from logistics and supply chain managers at US firms. Structural equation modelling was utilized to measure the statistical significance of the hypothesized model paths with all findings meeting the basic requirements of interpretation. Findings – The results suggest that logistics salience positively impacts both logistics innovativeness and logistics service differentiation. Logistics innovativeness and logistics service differentiation both positively influence logistics performance. These findings give credence to the resource based view of the firm which states that resources lead to capabilities which leads to performance. Research limitations/implications – Conclusions based on the study’s results highlight the importance of logistics within firms and indicate that the function must be made salient throughout the firm to further capitalize on the benefits of logistics. These benefits include enhanced logistics capabilities and their eventual impact on logistics performance. Originality/value – Using the resource based view of the firm as the theoretical framework, the manuscript supports the notion that logistics salience is an important resource for firms looking to provide differentiated services and innovative logistics operations to their customers

    Enhancing Dyadic Performance Through Boundary Spanners and Innovation: An Assessment of Service Provider–Customer Relationships

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    Firms recognize that working together through collaborative relationships offers potential benefits such as improving cooperation, information sharing, and overall performance. An additional and extremely valuable benefit of working together is the potential for creating innovative business approaches and solutions. Thus, developing external linkages has become a higher priority within many organizations. Boundary spanning employees offer one means of achieving closer cross‐firm relationships. We investigate the roles of boundary spanners by examining service providers and their relationships with customers. More specifically, we examine boundary spanning employees that are physically on‐site at customer facilities. Results provide strong support that boundary spanners perceiving higher levels of external organizational support from a client subsequently develop affective commitment to the customer. This, in turn, drives knowledge exchange and logistics innovation. A relationship between logistics innovation and performance (of service providers and of customers) was also found. Managerial implications of the research findings are discussed and suggestions presented covering future research

    Anisotropy in the Distribution of Galactic Radio Polarizations

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    Radiation traversing the observable universe provides powerful ways to probe anisotropy of electromagnetic propagation. A controversial recent study claimed a signal of dipole character. Here we test a new and independent data set of 361 points under the null proposal of {\it statistical independence} of linear polarization alignments relative to galaxy axes, versus angular positions. The null hypothesis is tested via maximum likelihood analysis of best fits among numerous independent types of factored distributions. We also examine single-number correlations which are parameter free, invariant under coordinate transformations, and distributed very robustly. The statistics are shown explicitly not to depend on the uneven distribution of sources on the sky. We find that the null proposal is not supported at the level of less than 5% to less than 0.1% by several independent statistics. The signal of correlation violates parity, that is, symmetry under spatial inversion, and requires a statistic which transforms properly. The data indicate an axis of correlation, on the basis of likelihood determined to be [R.A.=(0h,9m)±(1h,0m)[{\rm R.A.}=(0^{\rm h},9^{\rm m}) \pm (1^{\rm h},0^{\rm m}), Decl.=−1o±15o]{\rm Decl.} = -1^o\pm 15^o].Comment: 10 pages, Late

    Deeply Virtual Compton Scattering: How to Test Handbag Dominance?

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    We propose detailed tests of the handbag approximation in exclusive deeply virtual Compton scattering. Those tests make no use of any prejudice about parton correlations in the proton which are basically unknown objects and beyond the scope of perturbative QCD. Since important information on the proton substructure can be gained in the regime of light cone dominance we consider that such a class of tests is of special relevance

    QUANTIFICATION OF CATTAIL (\u3ci\u3eTYPHA\u3c/i\u3e SPP.) IN THE PRAIRIE POTHOLE REGION OF NORTH DAKOTA IN RELATION TO BLACKBIRD DAMAGE TO SUNFLOWER

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    Sunflower is an important crop for many farmers in the upper Midwest, especially in North Dakota and South Dakota. Blackbirds have been a major problem for the sunflower grower community. Bud depredation to a field can be devastating. The USDA-APHISWS is charged with reducing the conflict between the birds and the farmers. Many methods have been employed by Wildlife Services and other agencies to lessen the damage. One method is the reduction of the cattail (Typha spp.) habitat used by blackbirds in and around wetlands; however, cattails are used by other animals. Consequently, there is a need to insure habitat manipulation is not significantly affecting non-target species, hence knowing what portion of the total cattail habitat is being manipulated is critical. The purpose of this study was to quantify cattail habitat in the Prairie Pothole Region (PPR) of North Dakota. Remote sensing using aerial infrared photographs was used to sample 120, 10.36 km sq. plots, randomly distributed throughout each of four strata dividing the PPR in ND. ArcInfo 8x Geographic Information System (GIs) software was used to run a supervised classification to delineate cattail from other vegetation. Results found 2,245 =t 257 (S.E.) km sq. of cattail in the PPR. These findings show that less than one percent of the total cattail stand in the PPR is being affected by the USDA cattail management efforts
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