23,969 research outputs found

    General existence and uniqueness of viscosity solutions for impulse control of jump-diffusions

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    General theorems for existence and uniqueness of viscosity solutions for Hamilton-Jacobi-Bellman quasi-variational inequalities (HJBQVI) with integral term are established. Such nonlinear partial integro-differential equations (PIDE) arise in the study of combined impulse and stochastic control for jump-diffusion processes. The HJBQVI consists of an HJB part (for stochastic control) combined with a nonlocal impulse intervention term. Existence results are proved via stochastic means, whereas our uniqueness (comparison) results adapt techniques from viscosity solution theory. This paper is to our knowledge the first treating rigorously impulse control for jump-diffusion processes in a general viscosity solution framework; the jump part may have infinite activity. In the proofs, no prior continuity of the value function is assumed, quadratic costs are allowed, and elliptic and parabolic results are presented for solutions possibly unbounded at infinity

    Determination of the Thermodynamic Scaling Exponent from Static, Ambient-Pressure Quantities

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    An equation is derived that expresses the thermodynamic scaling exponent, g, which superposes relaxation times and other measures of molecular mobility determined over a range of temperatures and densities, in terms of static, physical quantities. The latter are available in the literature or can be measured at ambient pressure. We show for 13 materials, both molecular liquids and polymers, that the calculated g are equivalent to the scaling exponents obtained directly by superpositioning. The assumptions of the analysis are that the glass transition is isochronal and that the first Ehrenfest relation is valid; the first assumption is true by definition, while the second has been corroborated for many glass-forming materials at ambient pressure. However, we find that the Ehrenfest relation breaks down at elevated pressure, although this limitation is of no consequence herein, since the appeal of the new equation is its applicability to ambient pressure data.Comment: 9 pages, 3 figures, 1 tabl

    The Higgs as a Supersymmetric Partner, with a New Interpretation of Yukawa Couplings

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    An unconventional version of supersymmetry leads to the following highly testable predictions: (1) The Higgs boson has an R-parity of -1, so it can only be produced as one member of a pair of superpartners. (2) The only superpartners are scalar bosons, so neutralinos etc. do not exist. (3) The most likely candidate for cold dark matter is therefore a sneutrino. (4) The Higgs and other bosonic superpartners have an unconventional equation of motion. These predictions are associated with new interpretations of Yukawa couplings, supersymmetry, gauge fields, and Lorentz invariance.Comment: 4 pages, proceedings of DPF2000 Meeting of APS Division of Particles and Fields (August, 2000, Ohio State University

    Thermodynamic scaling of diffusion in supercooled Lennard-Jones liquids

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    The manner in which the intermolecular potential u(r) governs structural relaxation in liquids is a long standing problem in condensed matter physics. Herein we show that diffusion coefficients for simulated Lennard-Jones m-6 liquids (8<m<36) in normal and moderately supercooled states are a unique function of the variable rho^g/T, where rho is density and T is temperature. The scaling exponent g is a material specific constant whose magnitude is related to the steepness of the repulsive part of u(r), evaluated around the distance of closest approach between particles probed in the supercooled regime. Approximations of u(r) in terms of inverse power laws are also discussed.Comment: 4 pages, 3 figure

    The Timing of Climate Agreements under Multiple Externalities

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    We study the potential of cooperation in global emission abatements with multiple externalities. Using a two-country model without side-payments, we identify the strategic effects under different timing regimes of cooperation. We obtain a positive complementarity effect of long-term cooperation in abatement on R&D levels that boosts potential bene?t of long-term cooperation and a redistributive effect that destabilizes long-term cooperation when countries are asymmetric. We show that whether and what type of cooperation is sustainable, depends crucially on the kind rather than on the magnitude of asymmetries

    The Arts Economy in 20 Cities: Where Does Atlanta Stand?

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    The tremendous growth that Atlanta has experienced over the past decade has catapulted the city into a major metropolitan hub. Along with this growth, many issues have gained significance with regards to plans for the city's future direction of growth. One sector in particular that demands greater attention is the area of non-profit arts and art policy. The arts and culture have many perceived benefits for a community. The arts are commonly thought to improve a community's cultural life, revitalize urban areas, and while they also provide a base of support for artists and art organizations, may also ultimately stimulate economic growth. These benefits are thought to yield other desirable outcomes such as a safe and agreeable downtown, and an attractive site for business relocation.Unfortunately, non-profit regional arts in Atlanta have faced challenges in the areas of funding and audience development and there is anecdotal evidence that arts support is being provided by a relatively small segment of society. The Atlanta Arts Think Tank perceived that one appropriate way to validate the importance of these problems was to analyze data on Atlanta's regional performance, relative to other metropolitan peers.The purpose of this study is to gain a better understanding of the factors that might explain the condition of arts organizations in the region. The study compares Atlanta to nineteen of its peers in an attempt to determine where and if Atlanta is falling short, and what can be learned from other communities
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