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General Set (general + set)
Selected AbstractsFlux compactification of M-theory on compact manifolds with Spin(7) holonomy,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 11-12 2005D. Constantin At the leading order, M-theory admits minimal supersymmetric compactifications if the internal manifold has exceptional holonomy. The inclusion of non-vanishing fluxes in M-theory and string theory compactifications induce a superpotential in the lower dimensional theory, which depends on the fluxes. In this work, we check the conjectured form of this superpotential in the case of warped M-theory compactifications on Spin(7) holonomy manifolds. We perform a Kaluza-Klein reduction of the eleven-dimensional supersymmetry transformation for the gravitino and we find by direct comparison the superpotential expression. We check the conjecture for the heterotic string compactified on a Calabi-Yau three-fold as well. The conjecture can be checked indirectly by inspecting the scalar potential obtained after the compactification of M-theory on Spin(7) holonomy manifolds with non-vanishing fluxes. The scalar potential can be written in terms of the superpotential and we show that this potential stabilizes all the moduli fields describing deformations of the metric except for the radial modulus. All the above analyses require the knowledge of the minimal supergravity action in three dimensions. Therefore we calculate the most general causal ,, =1 three-dimensional, gauge invariant action coupled to matter in superspace and derive its component form using Ectoplasmic integration theory. We also show that the three-dimensional theory which results from the compactification is in agreement with the more general supergravity construction. The compactification procedure takes into account higher order quantum correction terms in the low energy effective action. We analyze the properties of these terms on a Spin(7) background. We derive a perturbative set of solutions which emerges from a warped compactification on a Spin(7) holonomy manifold with non-vanishing flux for the M-theory field strength and we show that in general the Ricci flatness of the internal manifold is lost, which means that the supergravity vacua are deformed away from the exceptional holonomy. Using the superpotential form we identify the supersymmetric vacua out of this general set of solutions. [source] Contiguity Constraints for Single-Region Site Search ProblemsGEOGRAPHICAL ANALYSIS, Issue 4 2000Thomas J. Cova This paper proposes an explicit set of constraints as a general approach to the contiguity problem in site search modeling. Site search models address the challenging problem of identifying the best area in a study region for a particular land use, given that there are no candidate sites. Criteria that commonly arise in a search include a site's area, suitability, cost, shape, and proximity to surrounding geographic features. An unsolved problem in this modeling arena is the identification of a general set of mathematical programming constraints that can guarantee a contiguous solution (site) for any 0,1 integer-programming site search formulation. The constraints proposed herein address this problem, and we evaluate their efficacy and efficiency in the context of a regular and irregular tessellation of geographic space. An especially efficient constraint form is derived from a more general form and similarly evaluated. The results demonstrate that the proposed constraints represent a viable, general approach to the contiguity problem. [source] High-dimensional model representation for structural reliability analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2009Rajib Chowdhury Abstract This paper presents a new computational tool for predicting failure probability of structural/mechanical systems subject to random loads, material properties, and geometry. The method involves high-dimensional model representation (HDMR) that facilitates lower-dimensional approximation of the original high-dimensional implicit limit state/performance function, response surface generation of HDMR component functions, and Monte Carlo simulation. HDMR is a general set of quantitative model assessment and analysis tools for capturing the high-dimensional relationships between sets of input and output model variables. It is a very efficient formulation of the system response, if higher-order variable correlations are weak, allowing the physical model to be captured by the first few lower-order terms. Once the approximate form of the original implicit limit state/performance function is defined, the failure probability can be obtained by statistical simulation. Results of nine numerical examples involving mathematical functions and structural mechanics problems indicate that the proposed method provides accurate and computationally efficient estimates of the probability of failure. Copyright © 2008 John Wiley & Sons, Ltd. [source] Costly State Verification with Varying Risk Preferences and LiabilityJOURNAL OF ECONOMIC SURVEYS, Issue 1 2006Gaia Garino Abstract., In the scenario of loan contracts with costly state verification, we examine how the properties of the set of states, different risk preferences of debtors and varying liability of lenders affect the structure of optimal repayments. In particular, we show that with risk-averse debtors, a general set of states, a constant observation cost and both unlimited and limited lender liability, the debtor is strictly better off revealing the true state of nature when his realized revenue is low, which implies that optimal debtor consumption has a downward jump around the single switch from observed to unobserved states. If the debtor can destroy revenue or if the debtor is risk neutral, this non-monotonicity of consumption disappears. Moreover, given the loan size, there is more monitoring under debtor-risk aversion than risk neutrality. We present simulations showing that a contract with unlimited lender liability and debtor-risk aversion has a higher expected observation cost but a lower variance of consumption than a contract with limited lender liability. Finally, we discuss the problems of commitment to verification and contract renegotiation in this framework. [source] Characterization of solvatochromic probes: simulation of merocyanine 540 absorption spectra in binary solvent mixtures and pure solvent systemsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2004S. Y. Bae Abstract An empirical extension of the continuum model was used to reproduce the absorption spectrum of the optical probe merocyanine 540 in numerous solvents based on 27 probe-specific parameters in conjunction with the dielectric constant and refractive index of the solvent. The calibrated absorption spectrum of this dye allowed the accurate determination of the dielectric constant and refractive index of the bulk solvent. This study incorporates several binary solvent mixtures in addition to several pure solvents of differing functionality, including protic and aprotic solvents. A single, generally applicable, set of probe-specific parameters is presented. The accuracy of the determined solvent properties using this general set of probe parameters suggests that the influence of specific solvent,solute interactions on the absorption spectrum of this dye must be constant if not insignificant in the range of solvents studied, with the notable exception of water. Copyright © 2004 John Wiley & Sons, Ltd. [source] Salamanca and the city: culture credits, nature credits, and the modern moral economy of indigenous BoliviaTHE JOURNAL OF THE ROYAL ANTHROPOLOGICAL INSTITUTE, Issue 2 2006Kathleen B. Lowrey This article draws on fieldwork carried out in a Guaraní-speaking community in the Bolivian Chaco , Isoso , between 1997 and 2000. At the time, some Isoseño people were employed in urban-headquartered projects that revolved around Isoso's environment, culture, or identity and that were funded multilaterally by grants, loans, or other foreign aid. The article describes a set of fantastic discourses circulating in rural Isoso that seem to compare a magical place called Salamanca to the city where some Isoseño people now work. The article argues that these Salamanca discourses are an Isoseño-specific way of talking about a general set of unprecedented processes. It takes up the fact that undertakings of the kind in which the Isoseño are involved create new calibrations among radically different systems for moral/qualitative and material/ quantitative evaluation which can most ,economically' be expressed in terms of credit and debt. Finally, it considers why it is that for all their strange magic, Isoseño ,Salamanca and the city' discourses put an extremely recognizable suite of moral considerations at their centre. [source] | ||||||||||