218,130 research outputs found

    Matching couples with Scarf's algorithm

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    Research-practice interactions as reported in recent design studies: Still promising, still hazy

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    This study portrays recent research–practice connections found in 18 design research reports focusing on the creation of instructional solutions. Solutions in different stages of development varied greatly in duration, ranging from one lesson to a whole year curriculum, spanned all levels of education, many subjects (science, math, language, culture, teacher education, etc.). Close collaboration between researchers and practitioners was prominent in all of the 18 projects studied. Participants in primary and secondary education projects have quite distinct roles regarding the teaching and researching, but they design their instruction solutions often collaboratively. Nearly all projects reported on how designed solutions were anchored in research, either from literature or from in-house project data. All articles indicated that research fed (re-)design, but few specified how. Based on our findings, we call for increased research and reporting on the specific strategies employed by design research participants to facilitate the production of new theoretical understanding through design of instructional solution

    AI for the Common Good?! Pitfalls, challenges, and Ethics Pen-Testing

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    Recently, many AI researchers and practitioners have embarked on research visions that involve doing AI for "Good". This is part of a general drive towards infusing AI research and practice with ethical thinking. One frequent theme in current ethical guidelines is the requirement that AI be good for all, or: contribute to the Common Good. But what is the Common Good, and is it enough to want to be good? Via four lead questions, I will illustrate challenges and pitfalls when determining, from an AI point of view, what the Common Good is and how it can be enhanced by AI. The questions are: What is the problem / What is a problem?, Who defines the problem?, What is the role of knowledge?, and What are important side effects and dynamics? The illustration will use an example from the domain of "AI for Social Good", more specifically "Data Science for Social Good". Even if the importance of these questions may be known at an abstract level, they do not get asked sufficiently in practice, as shown by an exploratory study of 99 contributions to recent conferences in the field. Turning these challenges and pitfalls into a positive recommendation, as a conclusion I will draw on another characteristic of computer-science thinking and practice to make these impediments visible and attenuate them: "attacks" as a method for improving design. This results in the proposal of ethics pen-testing as a method for helping AI designs to better contribute to the Common Good.Comment: to appear in Paladyn. Journal of Behavioral Robotics; accepted on 27-10-201

    The Effective Electroweak Chiral Lagrangian: The Matter Sector

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    We parametrize in a model-independent way possible departures from the minimal Standard Model predictions in the matter sector. We only assume the symmetry breaking pattern of the Standard Model and that new particles are sufficiently heavy so that the symmetry is non-linearly realized. Models with dynamical symmetry breaking are generically of this type. We review in the effective theory language to what extent the simplest models of dynamical breaking are actually constrained and the assumptions going into the comparison with experiment. Dynamical symmetry breaking models can be approximated at intermediate energies by four-fermion operators. We present a complete classification of the latter when new particles appear in the usual representations of the SU(2)L×SU(3)cSU(2)_L\times SU(3)_c group as well as a partial classification in the general case. We discuss the accuracy of the four-fermion description by matching to a simple `fundamental' theory. The coefficients of the effective lagrangian in the matter sector for dynamical symmetry breaking models (expressed in terms of the coefficients of the four-quark operators) are then compared to those of models with elementary scalars (such as the minimal Standard Model). Contrary to a somewhat widespread belief, we see that the sign of the vertex corrections is not fixed in dynamical symmetry breaking models. This work provides the theoretical tools required to analyze, in a rather general setting, constraints on the matter sector of the Standard Model.Comment: Latex, 45 pages, 8 eps figures. Sections 5, 6 and 9 have been rewritten to clarify the contents. Some mistakes and typos have been corrected. Two references have been added. Figures 7 and 8 have been modifie

    The Electroweak Chiral Lagrangian for the Standard Model with a Heavy Higgs

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    The most general chiral Lagrangian for electroweak interactions with the complete set of SU(2)L×U(1)YSU(2)_L\times U(1)_Y invariant operators up to dimension four is considered. The two-point and three-point functions with external gauge fields are derived from this effective chiral Lagrangian to one-loop order in a generic RΟR_\xi-gauge. The same set of Green's functions are paralelly studied in the renormalizable standard model to one-loop order, in a RΟR_\xi-gauge and in the large Higgs mass limit. An appropriate set of matching conditions connecting the Green's functions of the two theories allows us to derive, systematically, the values of the chiral Lagrangian coefficients corresponding to the large Higgs mass limit of the standard model. These chiral parameters represent the non-decoupling effects of a heavy Higgs particle and incorporate both the leading logarithmic dependence on \mh and the next to leading constant contributions. Some phenomenological implications are also discussed.Comment: pg.23, LaTeX, 3 figures (not included), FTUAM-93/2

    Vector Meson Masses in Chiral Perturbation Theory

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    We discuss the vector meson masses within the context of Chiral Perturbation Theory performing an expansion in terms of the momenta, quark masses and 1/Nc. We extend the previous analysis to include isospin breaking effects and also include up to order p4p^4. We discuss vector meson chiral perturbation theory in some detail and present a derivation from a relativistic lagrangian. The unknown coefficients are estimated in various ways. We also discuss the relevance of electromagnetic corrections and the implications of the present calculation for the determination of quark masses.Comment: 17 pages, LaTeX, 2 figures. Revised version to appear in Nuclear Physics B. One reference added, some misprints, mainly in the appendix, correcte
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