35,025 research outputs found

    Introduction

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    This issue of Library Trends, on the theme of Research Into Practice, has been designed with two aims in mind. Published in 2013, it marks the fiftieth anniversary of the founding of the Information School (iSchool) at the University of Sheffield in the United Kingdom by presenting a selection of papers that demonstrate the creativity and variety of research undertaken in the field of librarianship and share a unifying concern to make links, as well as establish meaningful connections, between research and practice. The issue is dedicated to Bob Usherwood, now an emeritus professor in the school, whose work and legacy at Sheffield are distinguished by an exemplary commitment to putting research into practice, and it is especially pleasing for us to be able offer this tribute to Bob in the year when he is due to celebrate his seventieth birthday. We also believe that an issue on this theme is timely and important for our profession. There has been a strong drive lately to promote evidence-based practice in library and information work and to develop a research culture in the practitioner community, exemplified in the United Kingdom by the DREaM project, amid continuing concerns about the disconnect between the research and practitioner communities

    High Temperature Asymptotics of Orthogonal Mean-Field Spin Glasses

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    We evaluate the high temperature limit of the free energy of spin glasses on the hypercube with Hamiltonian HN(σ)=σTJσH_N(\sigma) = \sigma^T J \sigma, where the coupling matrix JJ is drawn from certain symmetric orthogonally invariant ensembles. Our derivation relates the annealed free energy of these models to a spherical integral, and expresses the limit of the free energy in terms of the limiting spectral measure of the coupling matrix JJ. As an application, we derive the limiting free energy of the Random Orthogonal Model (ROM) at high temperatures, which confirms non-rigorous calculations of Marinari et al. (1994). Our methods also apply to other well-known models of disordered systems, including the SK and Gaussian Hopfield models.Comment: 15 pages, 1 figur

    Majorana Fermion Representation For An Antiferromagnetic Spin-1/2 Chain

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    We study the 1-dimensional Heisenberg antiferromagnet with s=1/2 using a Majorana representation of the s=1/2 spins. A simple Hartree-Fock approximation of the resulting model gives a bilinear fermionic description of the model. This description is rotationally invariant and gives power-law correlations in the ``ground state'' in a natural fashion. The excitations are a two-parameter family of particles, which are spin-1 objects. These are contrasted to the ``spinon'' spectrum, and the technical aspects of the representation are discussed, including the problem of redundant states.Comment: 24 pages in LaTeX, no figures; some clarifications/additions have been made following the referee's comments; to appear in Phys. Rev.

    Loop Variables and Gauge Invariant Interactions - I

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    We describe a method of writing down interacting equations for all the modes of the bosonic open string. It is a generalization of the loop variable approach that was used earlier for the free, and lowest order interacting cases. The generalization involves, as before, the introduction of a parameter to label the different strings involved in an interaction. The interacting string has thus becomes a ``band'' of finite width. The interaction equations expressed in terms of loop variables, has a simple invariance that is exact even off shell. A consistent definition of space-time fields requires the fields to be functions of all the infinite number of gauge coordinates (in addition to space time coordinates). The theory is formulated in one higher dimension, where the modes appear massless. The dimensional reduction that is needed to make contact with string theory (which has been discussed earlier for the free case) is not discussed here.Comment: 40 pages, Latex. Revised version: some typos corrected. Final version to appear in Int. J. of Mod. Phys.

    Background Independent Algebraic Structures in Closed String Field Theory

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    We construct a Batalin-Vilkovisky (BV) algebra on moduli spaces of Riemann surfaces. This algebra is background independent in that it makes no reference to a state space of a conformal field theory. Conformal theories define a homomorphism of this algebra to the BV algebra of string functionals. The construction begins with a graded-commutative free associative algebra \C built from the vector space whose elements are orientable subspaces of moduli spaces of punctured Riemann surfaces. The typical element here is a surface with several connected components. The operation Δ\Delta of sewing two punctures with a full twist is shown to be an odd, second order derivation that squares to zero. It follows that (\C, \Delta) is a Batalin-Vilkovisky algebra. We introduce the odd operator δ=+Δ\delta = \partial + \hbar\Delta, where \partial is the boundary operator. It is seen that δ2=0\delta^2=0, and that consistent closed string vertices define a cohomology class of δ\delta. This cohomology class is used to construct a Lie algebra on a quotient space of \C. This Lie algebra gives a manifestly background independent description of a subalgebra of the closed string gauge algebra.Comment: phyzzx.tex, MIT-CTP-234

    Acknowledgement Patterns in Research Articles: a Bibliometric Study based on Journal of Natural Rubber Research 1986-1997

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    Analyses the acknowledgements included in the research articles and short communications published in Journal of Natural Rubber Research (1986-1997) in respect of types, frequency of occurrence, individuals acknowledged, etc. Results indicate that 74% items contain acknowledgements; an average acknowledgement per item is 2.2; the most common type of acknowledgments relates to technical support. Peer interactive communication accounts for 44% of the total acknowledgements. The result of the study substantiates the earlier findings that a small number of individuals are highly acknowledged and the rest are acknowledged infrequently

    Proper Matter Collineations of Plane Symmetric Spacetimes

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    We investigate matter collineations of plane symmetric spacetimes when the energy-momentum tensor is degenerate. There exists three interesting cases where the group of matter collineations is finite-dimensional. The matter collineations in these cases are either four, six or ten in which four are isometries and the rest are proper.Comment: 10 pages, LaTex, accepted for publication in Modern Physics Letters

    Construction of some special subsequences within a Farey sequence

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    Recently it has been found that some special subsequences within a Farey sequence play a crucial role in determining the ranges of coupling constant for which quantum soliton states can exist for an integrable derivative nonlinear Schrodinger model. In this article, we find a novel mapping which connects two such subsequences belonging to Farey sequences of different orders. By using this mapping, we construct an algorithm to generate all of these special subsequences within a Farey sequence. We also derive the continued fraction expansions for all the elements belonging to a subsequence and observe a close connection amongst the corresponding expansion coefficients.Comment: latex, 8 page

    A String Motivated Approach to the Relativistic Point Particle

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    Using concepts developed in string theory, Cohen, Moore, Nelson and Polchinski calculated the propagator for a relativistic point particle. Following these authors we extend the technique to include the case of closed world lines. The partition function found corresponds to the Feynmann and Schwinger proper time formalism. We also explicitly verify that the partition function is equivalent to the usual path length action partition function. As an example of a sum over closed world lines, we compute the Euler-Heisenberg effective Lagrangian in a novel way.Comment: Talk at Balfest, Salerno 200
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