Phase Transitions and superuniversality in the dynamics of a self-driven particle

We study an active random walker model in which a particle's motion is determined by a self-generated field. The field encodes information about the particle's path history. This leads to either self-attractive or self-repelling behavior. For self-repelling behavior, we find a phase transition in the dynamics: when the coupling between the field and the walker exceeds a critical value, the particle's behavior changes from renormalized diffusion to one characterized by a diverging diffusion coefficient. The dynamical behavior for all cases is surprisingly independent of dimension and of the noise amplitude.Comment: 14 pages, 4 figure

Tilted accretion discs in cataclysmic variables: tidal instabilities and superhumps

We investigate the growth of tidal instabilities in accretion discs in a binary star potential, using three dimensional numerical simulations. As expected from analytic work, the disc is prone to an eccentric instability provided that it is large enough to extend to the 3:1 resonance. The eccentric disc leads to positive superhumps in the light curve. It has been proposed that negative superhumps might arise from a tilted disc, but we find no evidence that the companion gravitational tilt instability can grow fast enough in a fluid disc to create a measurable inclination. The origin of negative superhumps in the light curves of cataclysmic variables remains a puzzle.Comment: 7 pages, 7 figures, accepted for publication in MNRA

Managing soil biodiversity: The New Zealand experience

Species diversity is a very important component of a healthy soil ecosystem, and a necessary condition for long-term sustainable development. However, it is widely recognised that soil degradation and species extinction are on the increase in New Zealand, as land resources come under pressure from urban expansion and modern agribusiness. New Zealand's soils, flora and fauna have evolved many unique elements during their long isolation from other land masses. Habitat destruction and introduced plants and animals have, therefore, had increasingly detrimental effects on indigenous biodiversity. New Zealand must conserve what remains

Shaking the Foundations: A Reply to My Critics

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Modern International Thought: Problems and Prospects

International intellectual history—the intellectual history of the international and an internationalised intellectual history—has recently emerged as one of the most fertile areas of research in the history of ideas. This article responds to eight essays inspired by my own contribution to this field in Foundations of Modern International Thought (2013). It engages with their positive achievements regarding the recovery of other foundations for modern international thought: for example, in theology, historiography and gender history. It addresses some of the methodological problems arising from the search for foundations, notably anachronism, presentism and diffusionism. It expands on others’ arguments about the international thought of Hobbes and Locke and the limits of cosmopolitanism. Finally, it points the way forward for international intellectual history as a collaborative, interdisciplinary, transnational and transtemporal enterprise.Histor

What's the Big Idea? Intellectual History and the Longue Durée

Historians of all kinds are beginning to return to temporally expansive studies after decades of aversion and neglect. There are even signs that intellectual historians are returning to the longue durée. What are the reasons for this revival of long-range intellectual history? And how might it be rendered methodologically robust as well as historically compelling? This article proposes a model of transtemporal history, proceeding via serial contextualism to create a history in ideas spanning centuries, even millennia: key examples come from work in progress on ideas of civil war from ancient Rome to the present. The article concludes with brief reflections on the potential impact of the digital humanities on the practice of intellectual history.Histor

Historia Intelectual y Longue Durée. La Guerra Civil en Perspectiva Histórica

Resumen: Después de décadas de abandono, historiadores de todo tipo vuelven a ofrecer estudios de gran amplitud temporal. Hay signos de que los historiadores intelectuales están regresando incluso a la longue durée. ¿Cuáles son las razones de este revival de la historia de las ideas desde la larga duración? Este artículo propone un modelo de historia transtemporal, que procede por medio de un contextualismo seriado con el fin de crear una historia en ideas que puede abarcar siglos, incluso milenios: se ofrecen ejemplos clave procedentes de un trabajo en curso sobre las ideas acerca de la guerra civil desde la antigua Roma hasta el presente. El artículo concluye con unas breves reflexiones sobre el potencial impacto de las humanidades digitales en la práctica de la historia intelectual. Abstract: Historians of all kinds are beginning to return to temporally expansive studies after decades of aversion and neglect. There are even signs that intellectual historians are returning to the longue durée. What are the reasons for this revival of long-range intellectual history? And how might it be rendered methodologically robust as well as historically compelling? This article proposes a model of transtemporal history, proceeding via serial contextualism to create a history in ideas spanning centuries, even millennia: key examples come from work in progress on ideas of civil war from ancient Rome to the present. The article concludes with brief reflections on the potential impact of the digital humanities on the practice of intellectual history.Histor