28,815 research outputs found

    Mass Degeneracies In Self-Dual Models

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    An algebraic restriction of the nonabelian self-dual Chern-Simons-Higgs systems leads to coupled abelian models with interesting mass spectra. The vacua are characterized by embeddings of SU(2)SU(2) into the gauge algebra, and in the broken phases the gauge and real scalar masses coincide, reflecting the relation of these self-dual models to N=2N=2 SUSY. The masses themselves are related to the exponents of the gauge algebra, and the self-duality equation is a deformation of the classical Toda equations.Comment: 10 pages LaTeX (previous copy truncated

    The Euler-Heisenberg Lagrangian beyond one loop

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    We review what is presently known about higher loop corrections to the Euler-Heisenberg Lagrangian and its Scalar QED analogue. The use of those corrections as a tool for the study of the properties of the QED perturbation series is outlined. As a further step in a long-term effort to prove or disprove the convergence of the N photon amplitudes in the quenched approximation, we present a parameter integral representation of the three-loop Euler-Heisenberg Lagrangian in 1+1 dimensional QED, obtained in the worldline formalism.Comment: 11 pages, 2 figures, talk given by Christian Schubert at QFEXT11, Benasque, Spain, Sept. 18-24, 2011, to appear in the conference proceeding

    Supersymmetry Breaking with Periodic Potentials

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    We discuss supersymmetry breaking in some supersymmetric quantum mechanical models with periodic potentials. The sensitivity to the parameters appearing in the superpotential is more acute than in conventional nonperiodic models. We present some simple elliptic models to illustrate these points.Comment: 10 pp; Latex; 3 figures using eps

    Content Neutrality: A Defense

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    To date, both the United States federal government and twenty-one individual states have passed Religious Freedom Restoration Acts that aim to protect religious persons from having their sincere beliefs substantially burdened by governmental interests. RFRAs accomplish this by offering a three-pronged exemption test for religious objectors that is satisfied only when (1) an objector has a sincere belief that is being substantially burdened; (2) the government has a very good reason (e.g., health or safety) to interfere; and (3) there is a reasonable alternative to serve the compelling interest. Legal balancing tests like those found in RFRA are content neutral insofar as they sideline the belief-content of conscientious objections as irrelevant when determining the permissibility of granting legal accommodations. However, some theorists worry that this legal picture may be backward: perhaps balancing tests should be content non-neutral given the usual features of conscientious objections. For example, Yossi Nehushtan contends that, contrary to their typical codification, religious conscience beliefs seem undeserving of special legal accommodations because they possess uniquely strong empirical and theoretical ties to intolerance. Thus, the illiberally intolerant content of these conscientious objections might actually give the state a reason to refuse to grant legal exemptions. In this paper, I offer a cursory defense of content neutrality with respect to balancing tests like those found in RFRA. To begin, I outline Nehushtan’s argument for content non-neutrality. The cornerstone of his argument is that illiberal intolerance is intolerable such that conscientious objections that are based upon illiberally intolerant values provide the state with strong, normally prevailing reason not to grant an exemption. I argue that, even when the illiberally intolerant content of one’s conscience constitutes a weighty and relevant factor in determining the permissibility of granting a legal exemption, there remain significant problems. It is difficult, for example, to determine which views are illiberally intolerant and difficult to say whether illiberally intolerant views can effectively serve as the principled demarcating line in balancing tests. To conclude, I offer several cursory arguments in favor of adopting content-neutral approaches without necessarily making a comprehensive case. By drawing on the work of Amy Sepinwall, Nadia Sawicki, and Nathan Chapman, I show that content-neutral approaches can help to safeguard robust protections for conscience by permitting atypical exercises of conscience, protect minority thoughts and practices from being coercively supplanted by majoritarian understandings of morality, appropriately maintain the skepticism and humility that we owe each other as compatriots in a pluralistic society, and allow the kind of justifiable civil disobedience that has an important place in political history among other things

    An All-Orders Derivative Expansion

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    We evaluate the exact QED2+1QED_{2+1} effective action for fermions in the presence of a family of static but spatially inhomogeneous magnetic field profiles. This exact result yields an all-orders derivative expansion of the effective action, and indicates that the derivative expansion is an asymptotic, rather than a convergent, expansion.Comment: 9pp LaTeX; Talk at Telluride Workshop on Low Dimensional Field Theor

    The Irish Research electronic Library initiative – levelling the playing field?

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    Purpose - The Irish Research electronic Library (IReL) is a nationally funded electronic research library providing online access to full text articles from thousands of peer-reviewed publications in a range of disciplines. This paper examines the opportunities that have arisen for academic libraries at a local level in terms of how they expose resources and promote the initiative. It discusses the challenges that have arisen as libraries enhance, or indeed introduce, value added services to their research community. It examines the results of an in-depth national survey which yielded invaluable insights into how Irish researchers were using library services. Finally, it reflects on the challenges libraries face in facilitating and nurturing research behaviour. Design/methodology/approach – In the first quarter of 2007, seven university libraries asked their researchers for feedback on how they use IReL resources and their awareness of the initiative in the form of a national survey. These results and in particular the feedback from DCU researchers are further analysed. Focus groups and visits to research centres also provided more in-depth analysis. Findings- This paper finds that a collaborative approach to the negotiation of a single national licence for seven academic libraries, with associated training and a discount for consortium contracts has been highly successful. However, it has also posed significant challenges for all libraries in terms of ensuring that the resources are fully exploited and that the necessary support structures are in place to facilitate the provision of appropriate services to the growing research community. Originality/Value –This paper will be useful to libraries planning services for fourth level researchers and in particular, services that promote access to online resources

    Self-Dual Chern-Simons Theories

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    In these lectures I review classical aspects of the self-dual Chern-Simons systems which describe charged scalar fields in 2+12+1 dimensions coupled to a gauge field whose dynamics is provided by a pure Chern-Simons Lagrangian. These self-dual models have one realization with nonrelativistic dynamics for the scalar fields, and another with relativistic dynamics for the scalars. In each model, the energy density may be minimized by a Bogomol'nyi bound which is saturated by solutions to a set of first-order self-duality equations. In the nonrelativistic case the self-dual potential is quartic, the system possesses a dynamical conformal symmetry, and the self-dual solutions are equivalent to the static zero energy solutions of the equations of motion. The nonrelativistic self-duality equations are integrable and all finite charge solutions may be found. In the relativistic case the self-dual potential is sixth order and the self-dual Lagrangian may be embedded in a model with an extended supersymmetry. The self-dual potential has a rich structure of degenerate classical minima, and the vacuum masses generated by the Chern-Simons Higgs mechanism reflect the self-dual nature of the potential.Comment: 42 pages LaTe

    'We know them, but we don't know them': a grounded theory approach to exploring host students' perspectives on intercultural contact in an Irish university

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    This study is concerned with intercultural relations among students in an Irish university. Specifically, the study explores host culture students’ perceptions of cultural difference within the student body and their experiences of intercultural contact on campus, including the factors which inform such contact. Using a grounded theory approach, 24 in-depth qualitative interviews were conducted with 2nd year undergraduate students from three courses. The data were rigorously analysed through a systematic process of coding, categorisation and theoretical development to produce findings grounded in students’ personal comments and lived experiences. These findings indicate that although nationality and age are employed as markers of cultural identity, host students’ construction of cultural difference is heavily informed by their perception of diverging value systems within the specific educational environment. These values are in turn reflected in students’ reported behaviours, attitudes, and levels of engagement in the social and academic aspects of the university life. The findings also identify multiple situational and student-specific factors which impact upon the likelihood of students engaging in intercultural contact and their actual experiences of such contact, including factors impacting upon intercultural relational development. Furthermore, the study highlights the crucial role educational institutions can play in fostering intercultural contact among students and offers suggestions for promoting intercultural relations on campus. Overall, the findings indicate that host students perceive intercultural contact to be both complex and problematic. It is associated with heightened uncertainty and anxiety, and is commonly perceived to be more demanding, yet less rewarding, than intracultural contact. While students’ tendency to gravitate towards cultural peers represents a major obstacle to intercultural contact, language barriers and the need to adapt communication style also emerge as important issues affecting intercultural encounters. At a time when many Irish higher education institutions are experiencing significant diversification within the student body, this research is both timely and necessary

    Margin Squeeze: Theory, Practice, Policy

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    Margin squeeze occurs where the margin between the price charged by a vertically integrated firm for a wholesale input, and its own retail price for the end product incorporating the input, is so low as to foreclose one or more affected markets. The extent to which margin squeeze should constitute a discrete competition law offence, distinct from predation or refusal to deal, is a disputed question. A jurisprudential chasm between the approaches to margin squeeze under European Union competition law and United States antitrust has emerged, following the Court of Justice of the European Union’s judgments in Deutsche Telekom and TeliaSonera and the US Supreme Court’s decision in LinkLine. The EU recognises a broad concept of margin squeeze, applicable in any sector; the US does not recognise margin squeeze as a standalone abuse, and moreover, the presence of sector-specific regulation excludes the application of antitrust to the price levels that comprise the squeeze. This paper explores the margin squeeze concept, with particular attention to both areas of contention

    Collaboration on a grand scale: facilitating the transition of first year students into higher education

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    This article describes the development and delivery of a new research and study skills module delivered to all students in an undergraduate degree programme in Dublin City University. It discusses the benefits and challenges of successful collaboration between academics,librarians and other key support staff
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