17,703 research outputs found

    Library Cartoons: A Literature Review of Library-themed Cartoons, Caricatures, and Comics

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    To understand differing views of past events, historians, political science scholars, and sociologists have analyzed political and editorial cartoons with themes ranging from elections to fiscal policy to human rights. Yet scant research has been dedicated to cartoons with library themes. The author of this paper examines peer-reviewed literature on the subject of library cartoons, including historical background, analysis of recent themes, and arguments for promoting library-themed cartoons, caricatures, and comics. The author finds a significant gap in the literature on this topic and concludes that information professionals would benefit from a comprehensive content analysis of library-themed cartoons to enhance understanding of the significance of libraries during historic events, assess public perception of libraries, and identify trends over time

    Phenomenological hadron form factors: shape and relativity

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    The use of relativistic quark models with simple parametric wave functions for the understanding of the electromagnetic structure of nucleons together with their electromagnetic transition to resonances is discussed. The implications of relativity in the different ways it can be implemented in a simple model are studied together with the role played by mixed symmetry s-state and D-state deformations of the rest frame wave functions of the nucleon and Delta resonance.Comment: To appear in the proceedings of "Shape of Hadrons" workshop, Athens, Greece, 27-29 Apr 200

    The status of the Excited Baryon Analysis Center

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    The Excited Baryon Analysis Center (EBAC), which is associated with the Theory Group at Jefferson Laboratory, was initiated in 2006. Its main goal is to extract and interpret properties of nucleon resonances (N*) from the world data of meson production reactions induced by pions, photons and electrons. We review the main accomplishments of the center since then and sketch its near future perspectives.Comment: Invited plenary talk, to appear in the Proceedings of XIII International Conference on Hadron Spectroscopy, November 29 - December 4, 2009, Florida State University. (v2, references added, fig6 slightly modified

    Currents and Superpotentials in classical gauge theories: II. Global aspects and the example of Affine gravity

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    The conserved charges associated with gauge symmetries are defined at a boundary component of spacetime because the corresponding Noether current can be rewritten on-shell as the divergence of a superpotential. However, the latter is afflicted by ambiguities. Regge and Teitelboim found a procedure to lift the arbitrariness in the Hamiltonian framework. An alternative covariant formula was proposed by one of us for an arbitrary variation of the superpotential, it depends only on the equations of motion and on the gauge symmetry under consideration. Here we emphasize that in order to compute the charges, it is enough to stay at a boundary of spacetime, without requiring any hypothesis about the bulk or about other boundary components, so one may speak of holographic charges. It is well known that the asymptotic symmetries that lead to conserved charges are really defined at infinity, but the choice of boundary conditions and surface terms in the action and in the charges is usually determined through integration by parts, whereas each component of the boundary should be considered separately. We treat the example of gravity (for any spacetime dimension, with or without cosmological constant), formulated as an affine theory which is a natural generalization of the Palatini and Cartan-Weyl (vielbein) first-order formulations. We then show that the superpotential associated with a Dirichlet boundary condition on the metric (the one needed to treat asymptotically flat or AdS spacetimes) is the one proposed by Katz et al and not that of Komar. We finally discuss the KBL superpotential at null infinity

    Conformal internal symmetry of 2d2d σ\sigma-models coupled to gravity and a dilaton

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    General Relativity reduced to two dimensions possesses a large group of symmetries that exchange classical solutions. The associated Lie algebra is known to contain the affine Kac-Moody algebra A1(1)A_1^{(1)} and half of a real Witt algebra. In this paper we exhibit the full symmetry under the semi-direct product of \Lie{A_1^{(1)}} by the Witt algebra \Lie{\Wir}. Furthermore we exhibit the corresponding hidden gauge symmetries. We show that the theory can be understood in terms of an infinite dimensional potential space involving all degrees of freedom: the dilaton as well as matter and gravitation. In the dilaton sector the linear system that extends the previously known Lax pair has the form of a twisted self-duality constraint that is the analog of the self-duality constraint arising in extended supergravities in higher spacetime dimensions. Our results furnish a group theoretical explanation for the simultaneous occurrence of two spectral parameters, a constant one (=y=y) and a variable one (=t=t). They hold for all 2d2d non-linear σ\sigma-models that are obtained by dimensional reduction of G/HG/H models in three dimensions coupled to pure gravity. In that case the Lie algebra is \Lie{\Wir \semi G^{(1)}}; this symmetry acts on a set of off shell fields (in a fixed gauge) and preserves the equations of motion.Comment: 44 pages, LATE