52,127 research outputs found

    Resonances in the asteroid and trans-Neptunian belts: a brief review

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    Mean motion resonances play a fundamental role in the dynamics of the small bodies of the Solar System. The last decades of the 20th century gave us a detailed description of the dynamics as well as the process of capture of small bodies in coplanar or small inclination resonant orbits. More recently, semianalytical or numerical methods allowed us to explore the behavior of resonant motions for arbitrary inclination orbits. The emerging dynamics is very rich, including large orbital changes due to secular effects inside mean motion resonances. The process of capture in highly inclined or retrograde resonant orbits was addressed showing that the capture in retrograde resonances is more efficient than in direct ones. A new terminology appeared in order to characterize the properties of the resonances. Numerical explorations in the transneptunian region showed the relevance and the particular dynamics of the exterior resonances with Neptune which can account for some of the known high perihelion orbits in the scattered disk. Moreover, several asteroids evolving in resonance with planets other than Jupiter or Neptune were found and a large number of asteroids in three-body resonances were identified.Comment: Asteroids, Comets, Meteors 2017 meetin

    A note on graded hypersurface singularities

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    For a weighted quasihomogeneous two dimensional hypersurface singularity, we define a smoothing with unipotent monodromy and an isolated graded normal singularity. We study the natural weighted blow up of both the smoothing and the surface. In particular, we describe our construction for the quasihomogeneous singularities of type I, the 14 unimodal exceptional singularities and we relate it to their stable replacement.Comment: 19 pages, 4 figures. New section on stable replacement of Unimodal singularities, Several improvements and corrections. Comments welcom

    A framework for regulating microfinance institutions : the experience in Ghana and the Philippines

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    An earlier Policy Research Working Paper (Hennie van Greuning, Joselito Gallardo, and Bikki Randhawa,"A Framework for Regulating Microfinance Institutions,"WPS 2061, February 1999) presented a regulatory framework that identifies thresholds in financial intermediation activities that trigger a requirement for a microfinance institution to satisfy external or mandatory guidelines-a tiered approach to regulation and prudential supervision. The model focuses on risk-taking activities of microfinance institutions that must be managed and prudentially regulated. The author reports on the results of the field testing and assessment of the tiered approach, focusing on the experience of Ghana and the Philippines. The two countries both have a wide range of informal, semi-formal, and formal institutions providing financial services to the poor, but differ in how they regulate financial intermediation activities by microfinance providers. In his assessment and a comparative analysis, the author focuses on key issues in the regulatory and supervisory environment for microfinance-and in the legal system and judicial processes-being addressed by government authorities and microfinance stakeholders in both countries. He gives particular attention to the thresholds at which intermediation activities become subject to prudential regulation and regulatory standards for capitalization and capital adequacy, asset quality and provisioning for nonperforming loans, and liquidity management. seeks to identify the key elements and characteristics of the microfinance regulatory experience of Ghana and the Philippines and to draw the lessons that may be useful for other countries interested in establishing a regulatory environmentconducive to the development of sustainable microfinance institutions. The experience of Ghana and the Philippines shows that a transparent, inclusive regulatory framework is indispensable for enabling microfinance institutions to maintain market specialization and to pursue institutional development that leads to sustainability. Clear pathways for institutional transformation facilitate the integration of microfinance institutions into the formal financial system.Payment Systems&Infrastructure,Banks&Banking Reform,Rural Finance,Financial Intermediation,Decentralization,Banks&Banking Reform,Rural Finance,Financial Intermediation,Governance Indicators,Poverty Assessment

    The Relativistic Factor in the Orbital Dynamics of Point Masses

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    There is a growing population of relativistically relevant minor bodies in the Solar System and a growing population of massive extrasolar planets with orbits very close to the central star where relativistic effects should have some signature. Our purpose is to review how general relativity affects the orbital dynamics of the planetary systems and to define a suitable relativistic correction for Solar System orbital studies when only point masses are considered. Using relativistic formulae for the N body problem suited for a planetary system given in the literature we present a series of numerical orbital integrations designed to test the relevance of the effects due to the general theory of relativity in the case of our Solar System. Comparison between different algorithms for accounting for the relativistic corrections are performed. Relativistic effects generated by the Sun or by the central star are the most relevant ones and produce evident modifications in the secular dynamics of the inner Solar System. The Kozai mechanism, for example, is modified due to the relativistic effects on the argument of the perihelion. Relativistic effects generated by planets instead are of very low relevance but detectable in numerical simulations
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