25,959 research outputs found

    Black Hole Solution of Quantum Gravity

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    We present a spherically symmetric and static exact solution of Quantum Einstein Equations. This solution is asymptotically (for large rr) identical with the black hole solution on the anti--De Sitter background and, for some range of values of the mass possesses two horizons. We investigate thermodynamical properties of this solution.Comment: Plain Latex, 10 page

    Solutions of Quantum Gravity Coupled to the Scalar Field

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    We consider the Wheeler-De Witt equation for canonical quantum gravity coupled to massless scalar field. After regularizing and renormalizing this equation, we find a one-parameter class of its solutions.Comment: 8 pages, LaTe

    Ballistic transport: A view from the quantum theory of motion

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    Ballistic transport of electrons through a quantum wire with a constriction is studied in terms of Bohm's interpretation of quantum mechanics, in which the concept of a particle orbit is permitted. The classical bouncing ball trajectories, which justify the name ``ballistic transport'', are established in the large wave number limit. The formation and the vital role of quantum vortices is investigated.Comment: 14 pages, revtex, 4 postscript figure

    Topological Aspects of the Non-adiabatic Berry Phase

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    The topology of the non-adiabatic parameter space bundle is discussed for evolution of exact cyclic state vectors in Berry's original example of split angular momentum eigenstates. It turns out that the change in topology occurs at a critical frequency. The first Chern number that classifies these bundles is proportional to angular momentum. The non-adiabatic principal bundle over the parameter space is not well-defined at the critical frequency.Comment: 14 pages, Dep. of Physics, Uni. of Texas at Austin, Austin, Texas 78712, to appear in J. Physics

    Topological Black Holes in Quantum Gravity

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    We derive the black hole solutions with horizons of non-trivial topology and investigate their properties in the framework of an approach to quantum gravity being an extension of Bohm's formulation of quantum mechanics. The solutions we found tend asymptotically (for large rr) to topological black holes. We also analyze the thermodynamics of these space-times.Comment: 4pages, no figures, plain LaTe

    Fast growing instabilities for non-parallel flows

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    Unstable modes growing when two plasma shells cross over a background plasma at arbitrary angle θ\theta, are investigated using a non-relativistic three cold fluids model. Parallel flows with θ=0\theta=0 are slightly more unstable than anti-parallel ones with θ=π\theta=\pi. The case θ=π/2\theta=\pi/2 is as unstable as the θ=0\theta=0 one, but the fastest growing modes are oblique. While the most unstable wave vector varies with orientation, its growth rate slightly evolves and there is no such thing as a stable configuration. A number of exact results can be derived, especially for the θ=π/2\theta=\pi/2 case.Comment: 4 pages, 3 figures, to appear in Phys. Lett.

    Quantum Adiabatic Approximation, Quantum Action, and Berry's Phase

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    An alternative interpretation of the quantum adiabatic approximation is presented. This interpretation is based on the ideas originally advocated by David Bohm in his quest for establishing a hidden variable alternative to quantum mechanics. It indicates that the validity of the quantum adiabatic approximation is a sufficient condition for the separability of the quantum action function in the time variable. The implications of this interpretation for Berry's adiabatic phase and its semi-classical limit are also discussed.Comment: uuencoded LaTeX file, 5 page

    Statistics of weighted Poisson events and its applications

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    The statistics of the sum of random weights where the number of weights is Poisson distributed has important applications in nuclear physics, particle physics and astrophysics. Events are frequently weighted according to their acceptance or relevance to a certain type of reaction. The sum is described by the compound Poisson distribution (CPD) which is shortly reviewed. It is shown that the CPD can be approximated by a scaled Poisson distribution (SPD). The SPD is applied to parameter estimation in situations where the data are distorted by resolution effects. It performs considerably better than the normal approximation that is usually used. A special Poisson bootstrap technique is presented which permits to derive confidence limits for observations following the CPD.Comment: 14 pages, 2 figure

    Improving Cost-effectiveness and Facilitating Participation of Developing Countries in International Emissions Trading

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    This paper discusses ways in which the next climate agreement ­ a renegotiated Kyoto Protocol or a second-period agreement ­ can be made more cost-effective. The discussion focuses on the design of international emissions trading to facilitate early participation by developing countries. Four aspects are highlighted: the design of compensation rules, the need to regulate the use of the CDM, the effect of allowing borrowing and the implications of a Commitment Period Reserve.Climate change policy; cost effectiveness; international emissions trading; Kyoto protocol; Clean Development Mechanism; Commitment Period Reserve; developing countries
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