101,710 research outputs found

    BPS states of curves in Calabi--Yau 3--folds

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    The Gopakumar-Vafa conjecture is defined and studied for the local geometry of a curve in a Calabi-Yau 3-fold. The integrality predicted in Gromov-Witten theory by the Gopakumar-Vafa BPS count is verified in a natural series of cases in this local geometry. The method involves Gromov-Witten computations, Mobius inversion, and a combinatorial analysis of the numbers of etale covers of a curve.Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol5/paper9.abs.html Version 3 is GT version 2 and has corrections to eq (2) on p 295, to 1st eq in Prop 2.1 and the tables on p 39

    Contempt, Community, and the Interruption of Sense

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    In the early modern period, contempt emerged as a persistent theme in moral philosophy. Most of the moral philosophers of the period shared two basic commitments in their thinking about contempt. First, they argued that we understand the value of others in the morally appropriate way when we understand them from the perspective of the morally relevant community. And second, they argued that we are naturally inclined to judge others as contemptible, and that we must therefore interrupt that natural movement of sense-bestowal in order to value others in the morally appropriate way. In this paper I examine in detail the arguments of Nicolas Malebranche and Immanuel Kant concerning the wrongness of contempt, emphasizing the ways in which they depend on conceptions of community and of the interruption of moral sense-bestowal. After showing how each of these arguments fails to comprehend the nature and the wrongness of contempt, I argue that we can find the resources for a more adequate account in the work of Jean-Luc Nancy, and specifically in his reflections on ontology and on the meaning of communit

    A boundary integral method for an inverse problem in thermal imaging

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    An inverse problem in thermal imaging involving the recovery of a void in a material from its surface temperature response to external heating is examined. Uniqueness and continuous dependence results for the inverse problem are demonstrated, and a numerical method for its solution is developed. This method is based on an optimization approach, coupled with a boundary integral equation formulation of the forward heat conduction problem. Some convergence results for the method are proved, and several examples are presented using computationally generated data

    Designing a Mixed Public and Private System for the Health Insurance Market

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    Reviews features of a reform proposal offering both public and private plans in a government-run purchasing pool, modeled on Medicare, in the commercial insurance market. Analyzes potential issues, including standardization of benefits and risk selection

    Two Nations Under God

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    Review of The World Bank, A Case for Aid: Building a Consensus for Development Assistance, by James D. Wolfensohn & Nicolas Stern

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    [Excerpt] The World Bank’s new book, A Case for Aid: Building a Consensus for Development Assistance, indicates how dramatic and lasting the progress against global poverty has been in the past 50 years. It also shows how dramatically the Bank’s own understanding has risen, even in the past decade, of how to make its efforts more effective in relieving poverty and achieving other development goals. These two themes form the basis for the World Bank’s visionary thesis: that eradicating much of the poverty, ill health, and illiteracy around the world is within reach. The occasion for pronouncing this message in A Case for Aid was the International Conference on Financing for Development, held in Monterrey, Mexico in March 2002. The United Nations hosted this conference to chart the future of foreign aid. The conference was notable in part because of the dramatic, and surprising to some, announcement by America’s President Bush of a bold new commitment by the United States to foreign aid for the developing world. A Case for Aid memorializes this conference, and provides analysis and commentary of its issues. It includes four parts. First is a keynote speech, “A Partnership for Development and Peace,” from World Bank president James D. Wolfensohn. Second is an essay, “Making the Case for Aid,” written by World Bank chief economist Nicolas Stern after the conference. Third, forming the book’s bulk, is “The Role and Effectiveness of Development Assistance,” by a panel of World Bank authors. Finally, the book includes the official U.N. document “The Monterrey Consensus.
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