14,030 research outputs found

    Deformations of Cosmological Solutions of D=11 Supergravity

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    We study Lunin-Maldacena deformations of cosmological backgrounds of D=11 supergravity which gives an easy way to generate solutions with nonzero 4-form flux starting from solutions of pure Einstein equations which possess at least three U(1) isometries. We illustrate this on the vacuum S-brane solution from which the usual SM2-brane solution is obtained. Applying the method again, one either gets the recently found S-brane system where contribution of the Chern-Simons term to field equations is non-zero or the SM2-SM2(0) intersection, depending on which U(1) directions are used during the process. Repeated usage of the procedure gives rise to configurations with several overlapping S-branes some of which are new. We also employ this method to construct two more new solutions and make comments about accelerating cosmologies that follow from such deformed solutions after compactification to (1+3)-dimensions.Comment: v2:some comments and references adde

    What Were They Thinking? The Federal Reserve In The Run-Up To The 2008 Financial Crisis

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    The Federal Reserve (the Fed) is responsible for monitoring, analyzing and ultimately stabilizing US financial markets. It also has unrivalled access to economic data, high-level connections to financial institutions, and a large staff of professionally trained economists. Why then was it apparently unconcerned by the financial developments that are now widely recognized to have caused the 2008 financial crisis? Using a wide range of Fed documents from the pre-crisis period, particularly the transcripts of meetings of the Federal Open Market Committee (FOMC), this paper shows that Fed policymakers and staff were aware of relevant developments in financial markets, but paid infrequent attention to them and disregarded significant systemic threats. Drawing on literatures in economics, political science and sociology, the paper then demonstrates that the Fed\u27s intellectual paradigm in the years before the crisis focused on ‘post hoc interventionism’ – the institution\u27s ability to limit the fallout should a systemic disturbance arise. Further, the paper argues that institutional routines played a crucial role in maintaining this paradigm and in contributing to the Fed\u27s inadequate attention to the warning signals in the pre-crisis period

    Evolving temporal fuzzy association rules from quantitative data with a multi-objective evolutionary algorithm

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    A novel method for mining association rules that are both quantitative and temporal using a multi-objective evolutionary algorithm is presented. This method successfully identifies numerous temporal association rules that occur more frequently in areas of a dataset with specific quantitative values represented with fuzzy sets. The novelty of this research lies in exploring the composition of quantitative and temporal fuzzy association rules and the approach of using a hybridisation of a multi-objective evolutionary algorithm with fuzzy sets. Results show the ability of a multi-objective evolutionary algorithm (NSGA-II) to evolve multiple target itemsets that have been augmented into synthetic datasets

    Environmental urbanization assessment using gis and multicriteria decision analysis: a case study for Denizli (Turkey) municipal area

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    In recent years, life quality of the urban areas is a growing interest of civil engineering. Environmental quality is essential to display the position of sustainable development and asserts the corresponding countermeasures to the protection of environment. Urban environmental quality involves multidisciplinary parameters and difficulties to be analyzed. The problem is not only complex but also involves many uncertainties, and decision-making on these issues is a challenging problem which contains many parameters and alternatives inherently. Multicriteria decision analysis (MCDA) is a very prepotent technique to solve that sort of problems, and it guides the users confidence by synthesizing that information. Environmental concerns frequently contain spatial information. Spatial multicriteria decision analysis (SMCDA) that includes Geographic Information System (GIS) is efficient to tackle that type of problems. This study has employed some geographic and urbanization parameters to assess the environmental urbanization quality used by those methods. The study area has been described in five categories: very favorable, favorable, moderate, unfavorable, and very unfavorable. The results are momentous to see the current situation, and they could help to mitigate the related concerns. The study proves that the SMCDA descriptions match the environmental quality perception in the city. © 2018 Erdal Akyol et al
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