13,789 research outputs found

    Theory of Weak Hypernuclear Decay

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    The weak nonmesonic decay of Lambda-hypernuclei is studied in the context of a one-meson-exchange model. Predictions are made for the decay rate, p/n stimulation ratio and the asymmetry in polarized hypernuclear decay.Comment: Standard 41 page Latex fil

    Quantum diffusion on a cyclic one dimensional lattice

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    The quantum diffusion of a particle in an initially localized state on a cyclic lattice with N sites is studied. Diffusion and reconstruction time are calculated. Strong differences are found for even or odd number of sites and the limit N->infinit is studied. The predictions of the model could be tested with micro - and nanotechnology devices.Comment: 17 pages, 5 figure

    Intrinsic switching field distribution of arrays of Ni80Fe20 nanowires probed by in situ\mathit{in\, situ} magnetic force microscopy

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    The progress of magnetization reversal of weakly packed ferromagnetic Ni80Fe20 nanowire arrays of different diameters (40, 50, 70 and 100 nm) electrodeposited in polycarbonate membranes was studied by magnetic force microscopy (MFM). For such a low packing density of nanomagnets, the dipolar interactions between neighbouring wires can be neglected. The intrinsic switching field distribution has been extracted from in situ MFM images and its width was found to be considerably smaller than for densely packed nanowire arrays.Comment: 4 pages, 5 figures. To appear in Journal of Superconductivity and Novel Magnetis

    Partial and Complete Observables for Hamiltonian Constrained Systems

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    We will pick up the concepts of partial and complete observables introduced by Rovelli in order to construct Dirac observables in gauge systems. We will generalize these ideas to an arbitrary number of gauge degrees of freedom. Different methods to calculate such Dirac observables are developed. For background independent field theories we will show that partial and complete observables can be related to Kucha\v{r}'s Bubble Time Formalism. Moreover one can define a non-trivial gauge action on the space of complete observables and also state the Poisson brackets of these functions. Additionally we will investigate, whether it is possible to calculate Dirac observables starting with partially invariant partial observables, for instance functions, which are invariant under the spatial diffeomorphism group.Comment: 38 page

    Magnetic force microscopy investigation of arrays of nickel nanowires and nanotubes

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    The magnetic properties of arrays of nanowires (NWs) and nanotubes (NTs), 150 nm in diameter, electrodeposited inside nanoporous polycarbonate membranes are investigated. The comparison of the nanoscopic magnetic force microscopy (MFM) imaging and the macroscopic behavior as measured by alternating gradient force magnetometry (AGFM) is made. It is shown that MFM is a complementary technique that provides an understanding of the magnetization reversal characteristics at the microscopic scale of individual nanostructures. The local hysteresis loops have been extracted by MFM measurements. The influence of the shape of such elongated nanostructures on the dipolar coupling and consequently on the squareness of the hysteresis curves is demonstrated. It is shown that the nanowires exhibit stronger magnetic interactions than nanotubes. The non-uniformity of the magnetization states is also revealed by combining the MFM and AGFM measurements.Comment: 7 pages, 5 figure

    On Unitary Evolution of a Massless Scalar Field In A Schwarzschild Background: Hawking Radiation and the Information Paradox

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    We develop a Hamiltonian formalism which can be used to discuss the physics of a massless scalar field in a gravitational background of a Schwarzschild black hole. Using this formalism we show that the time evolution of the system is unitary and yet all known results such as the existence of Hawking radiation can be readily understood. We then point out that the Hamiltonian formalism leads to interesting observations about black hole entropy and the information paradox.Comment: 45 pages, revte

    Global Citizenship and Business Education, Part 1: Antecedents and Foundations

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    Whereas national sovereignty persists as the primary form of political organization, the interconnectedness of today's world implies that any citizen's rights and obligations are no longer confined within national boundaries while many societal issues require global civic responses. Thus, business leaders need to be educated on the skills and values that characterize global citizenship in order for them to be accountable and act accordingly. This article traces the historical foundations of the concept of global citizenship, its definition and legitimacy. We also list the major skills and values that global citizens must possess in order to act accordingly

    Global Citizenship and Business Education, Part 2: The Role of Business Schools

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    Over the last decade we have seen increased demands for full stakeholder models in global decision-making and greater emphasis by accrediting agencies that business schools show their commitment to societal ends. The COVID-19 pandemic has brought these issues to the fore. We trace early developments in how business schools dealt with these demands and analyze the data from the Aspen Institute's survey of business schools' commitment to global citizenship programs. We then review more recent efforts and report on several institutional and collaborative efforts to promote a global citizenship agenda among business schools and their curricula
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