3,947 research outputs found

    Danger on the Exchange: How Counterparty Risk Was Managed on the Paris Bourse in the Nineteenth Century

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    Over the course of the nineteenth century, the struggles of Paris Bourse to manage counterparty risk revealed the awkward choices that face derivatives exchanges. Shortly after it was founded, the stock exchange, primarily a forward market, instituted a mutual guarantee fund to prevent broker failures from snowballing into a general liquidity crisis. The creation of the fund then forced the Bourse to search for mechanisms to control moral hazard. To study the determinants of broker failures, we collected new individual data on defaulting brokers and describe the evolving regulatory regime. To identify the factors behind the annual number of broker failures we use negative binominal regressions. To explain individual brokers’ duration in office, we employ a proportional hazard model, while logit regressions examine the causes of individual broker failures. In addition to declines in asset prices and trading volume, the moral hazard from the mutual guarantee fund contributed to brokers’ defaulting on their obligations. The Bourse faced a conundrum; when it finally imposed a tight regulatory regime that limited risk, trading began to migrate off the exchange to less regulated markets.

    Signals of Inflation in a Friendly String Landscape

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    Following Freivogel {\it et al} we consider inflation in a predictive (or `friendly') region of the landscape of string vacua, as modeled by Arkani-Hamed, Dimopoulos and Kachru. In such a region the dimensionful coefficients of super-renormalizable operators unprotected by symmetries, such as the vacuum energy and scalar mass-squareds are freely scanned over, and the objects of study are anthropically or `environmentally' conditioned probability distributions for observables. In this context we study the statistical predictions of (inverted) hybrid inflation models, where the properties of the inflaton are probabilistically distributed. We derive the resulting distributions of observables, including the deviation from flatness 1Ω|1-\Omega|, the spectral index of scalar cosmological perturbations nsn_s (and its scale dependence dns/dlogkdn_s/d\log k), and the ratio of tensor to scalar perturbations rr. The environmental bound on the curvature implies a solution to the η\eta-problem of inflation with the predicted distribution of (1ns)(1-n_s) indicating values close to current observations. We find a relatively low probability (<3<3%) of `just-so' inflation with measurable deviations from flatness. Intermediate scales of inflation are preferred in these models.Comment: 20 pages, 11 figure

    Edge States and Topological Pumping in Stiffness Modulated Elastic Plates

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    We demonstrate that modulations of the stiffness properties of an elastic plate along a spatial dimension induce edge states spanning non-trivial gaps characterized by integer valued Chern numbers. We also show that topological pumping is induced by smooth variations of the phase of the modulation profile along one spatial dimension, which results in adiabatic edge-to-edge transitions of the edge states. The concept is first illustrated numerically for sinusoidal stiffness modulations, and then experimentally demonstrated in a plate with square-wave thickness profile. The presented numerical and experimental results show how continuous modulations of properties may be exploited in the quest for topological phases of matter. This opens new possibilities for topology-based waveguiding through slow modulations along a second dimension, spatial or temporal

    Eguaglianza e dignit&#224; umana

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    Rawls, il merito e la meritocrazia

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    Dopo una rapida analisi delle nozioni di merito e di meritocrazia, il saggio esamina la teoria della giustizia come equit\ue0 al fine di verificare la tesi di Rawls secondo cui quella teoria non condurrebbe a un assetto sociale meritocratico. Nel far ci\uf2 il saggio si sofferma in particolare a esaminare le implicazioni della teoria di Rawls per quanto riguarda la selezione delle persone cui assegnare impieghi e incarichi. Il saggio, inoltre, ricostruisce l\u2019argomento con cui Rawls esclude che vi sia alcun dovere etico fondamentale di attribuire certi beni in un modo che tenga conto dei meriti delle persone e sostiene che un tale argomento non sia in grado di escludere l\u2019esistenza di un dovere etico fondamentale di distribuire il prodotto del lavoro sociale in un modo che tenga conto, almeno in parte, dell\u2019impegno delle persone e del loro contributo al benessere della collettivit\ue0.After a brief analysis of the notions of merit and meritocracy, the paper examines the theory of justice as fairness in order to assess Rawls\u2019s claim that his theory would not lead to a meritocratic society. In doing so, the paper focuses in particular on the implications of Rawls\u2019s theory regarding the allocation of jobs. The essay also reconstructs the argument Rawls uses to justify his claim that there is no fundamental ethical duty to assign certain goods in a way that takes into account the merits of people and argues that such an argument cannot exclude the existence of a fundamental ethical duty to distribute the product of social cooperation in a way that takes into account, at least in part, people\u2019s efforts and their contribution to the welfare of the community

    Magpie: towards a semantic web browser

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    Web browsing involves two tasks: finding the right web page and then making sense of its content. So far, research has focused on supporting the task of finding web resources through ‘standard’ information retrieval mechanisms, or semantics-enhanced search. Much less attention has been paid to the second problem. In this paper we describe Magpie, a tool which supports the interpretation of web pages. Magpie offers complementary knowledge sources, which a reader can call upon to quickly gain access to any background knowledge relevant to a web resource. Magpie automatically associates an ontologybased semantic layer to web resources, allowing relevant services to be invoked within a standard web browser. Hence, Magpie may be seen as a step towards a semantic web browser. The functionality of Magpie is illustrated using examples of how it has been integrated with our lab’s web resources
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