59 resultados para Hill Instability


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This paper examines the implications of ‘cultural defence’ in the nature of democracy and the stability of the political system in Greece. It focuses on the Greek Orthodox Church’s maintenance of power and political relevance by virtue of its strong link to national identity. We argue that the inhibition of secularization in Greece as a result of cultural defence has significant policy implications, especially in times of crises, when the role of nationalism as a cohesive factor against perceived threats is intensified. The paper further explores three policy/politics areas: (1) political orientation; (2) religious pluralism; and (3) education.

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We investigate baroclinic instability in flow conditions relevant to hot extrasolar planets. The instability is important for transporting and mixing heat, as well as for influencing large-scale variability on the planets. Both linear normal mode analysis and non-linear initial value cal- culations are carried out – focusing on the freely-evolving, adiabatic situation. Using a high- resolution general circulation model (GCM) which solves the traditional primitive equations, we show that large-scale jets similar to those observed in current GCM simulations of hot ex- trasolar giant planets are likely to be baroclinically unstable on a timescale of few to few tens of planetary rotations, generating cyclones and anticyclones that drive weather systems. The growth rate and scale of the most unstable mode obtained in the linear analysis are in qual- itative, good agreement with the full non-linear calculations. In general, unstable jets evolve differently depending on their signs (eastward or westward), due to the change in sign of the jet curvature. For jets located at or near the equator, instability is strong at the flanks – but not at the core. Crucially, the instability is either poorly or not at all captured in simulations with low resolution and/or high artificial viscosity. Hence, the instability has not been observed or emphasized in past circulation studies of hot extrasolar planets.

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Factor forecasting models are shown to deliver real-time gains over autoregressive models for US real activity variables during the recent period, but are less successful for nominal variables. The gains are largely due to the Financial Crisis period, and are primarily at the shortest (one quarter ahead) horizon. Excluding the pre-Great Moderation years from the factor forecasting model estimation period (but not from the data used to extract factors) results in a marked fillip in factor model forecast accuracy, but does the same for the AR model forecasts. The relative performance of the factor models compared to the AR models is largely unaffected by whether the exercise is in real time or is pseudo out-of-sample.

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Utterance of a sentence in poetry can be performative, and explicitly so. The best-known of Geoffrey Hill’s critical essays denies this, but his own poetry demonstrates it. I clarify these claims and explain why they matter. What Hill denies illuminates anxieties about responsibility and commitment that poets and critics share with philosophers. What Hill demonstrates affords opportunities for mutual benefit between philosophy and criticism.

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This article examines the role played by ideas and their thinkers in Christopher Hill's histories of the English Revolution. Hill protested against a reductionist economic determinism with no place for the intrinsic power of ideas, but his account of ideas gave them a progressive logic parallel to, if not always easy to link with, that of economic development, and threatened to divorce them from their muddled and imperfect thinkers. This account of the logic of ideas had a striking impact on the way in which the more mainstream radicals of the English Revolution appeared in Hill's work, with both the Levellers and James Harrington being half assimilated to, and half pushed aside in favor of, the more thoroughgoing economic radicals who expressed, in however ragged a way, the intrinsic potential of their ideas. However, Hill's writings also betray a surprising attraction to religious over secular forms of radicalism.