18 research outputs found

    Dynamic Responsiveness in the U.S. Senate

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    I develop a theory of dynamic responsiveness that suggests that parties that win elections choose candidates who are more extreme and parties that lose elections choose candidates who are more moderate. Moreover, the size of past victories matters. Close elections yield little change, but landslides yield larger changes in the candidates offered by both parties. I test this theory by analyzing the relationship between Republican vote share in U.S. Senate elections and the ideology of candidates offered in the subsequent election. The results show that Republican (Democratic) victories in past elections yield candidates who are more (less) conservative in subsequent elections, and the effect is proportional to the margin of victory. This suggests that parties or candidates pay attention to past election returns. One major implication is that parties may remain polarized in spite of their responsiveness to the median voter

    Axisymmetric Modes in Magnetic Flux Tubes with Internal and External Magnetic Twist

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    © 2015. The American Astronomical Society. All rights reserved. Observations suggest that twisted magnetic flux tubes are ubiquitous in the Sun's atmosphere. The main aim of this work is to advance the study of axisymmetric modes of magnetic flux tubes by modeling both twisted internal and external magnetic fields, when the magnetic twist is weak. In this work, we solve the derived wave equations numerically assuming that the twist outside the tube is inversely proportional to the distance from its boundary. We also study the case of a constant magnetic twist outside the tube and solve these equations analytically. We show that the solution for a constant twist outside the tube is a good approximation for the case where the magnetic twist is proportional to , namely, the error is in all cases less than . The solution is in excellent agreement with solutions to simpler models of twisted magnetic flux tubes, i.e., without external magnetic twist. It is shown that axisymmetric Alfvén waves are naturally coupled with magnetic twist as the azimuthal component of the velocity perturbation is nonzero. We compared our theoretical results with observations and comment on what the Doppler signature of these modes is expected to be. Lastly, we argue that the character of axisymmetric waves in twisted magnetic flux tubes can lead to false positives in identifying observations with axisymmetric Alfvén waves

    Environment-security nexus in northeast Asia

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    The concept of environmental security, under the umbrella of regional comprehensive security, provides a common framework to support bilateral as well as multilateral initiatives on the nexus of environment-security issues in Northeast Asia. These initiatives could provide the foundation upon which a common understanding and language, and common interests can be constructed on regional environmental and security issues. A consensus is to be built among key thinkers and opinion-makers in the region. Attention is needed to the security implications of regional-scale environmental degradation, and regional energy and environmental cooperation to address this degradation, thereby enhancing the multilateral institution-building process in Northeast Asia. As in traditional security arena, the United States needs to take the leadership role in the management of environmental problems in Northeast Asia. While maintaining the U.S.-Japan-South Korea cooperation as a central axis for environmental security of Northeast Asia, the United States needs to formulate a clearly articulated, coherent China policy with explicit objectives and guidelines by which progress on a variety of issues could be measured.
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