1,892 research outputs found

    Timelike deeply virtual Compton scattering with a linearly polarized real (or quasi-real) photon beam

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    We calculate timelike virtual Compton scattering amplitudes in the generalized Bjorken scaling regime and focus on a new polarization asymmetry in the scattering process with a linearly polarized photon beam in the medium energy range, which will be studied intensely at JLab12 experiments. We demonstrate that new observables help us to access the polarized quark and gluon generalized parton distributions H~(x,ξ,t)\tilde H(x, \xi, t) and E~(x,ξ,t) \tilde E(x, \xi, t).Comment: To appear in the proceedings XXII. International Workshop on Deep Inelastic Scattering and Related Subjects (DIS 2014), 28 April - 2 May 2014, Warsaw, Polan

    Triangle-free geometric intersection graphs with large chromatic number

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    Several classical constructions illustrate the fact that the chromatic number of a graph can be arbitrarily large compared to its clique number. However, until very recently, no such construction was known for intersection graphs of geometric objects in the plane. We provide a general construction that for any arc-connected compact set XX in R2\mathbb{R}^2 that is not an axis-aligned rectangle and for any positive integer kk produces a family F\mathcal{F} of sets, each obtained by an independent horizontal and vertical scaling and translation of XX, such that no three sets in F\mathcal{F} pairwise intersect and χ(F)>k\chi(\mathcal{F})>k. This provides a negative answer to a question of Gyarfas and Lehel for L-shapes. With extra conditions, we also show how to construct a triangle-free family of homothetic (uniformly scaled) copies of a set with arbitrarily large chromatic number. This applies to many common shapes, like circles, square boundaries, and equilateral L-shapes. Additionally, we reveal a surprising connection between coloring geometric objects in the plane and on-line coloring of intervals on the line.Comment: Small corrections, bibliography updat

    Dimension is polynomial in height for posets with planar cover graphs

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    We show that height~hh posets that have planar cover graphs have dimension O(h6)O(h^6). Previously, this upper bound was 2O(h3)2^{O(h^3)}. Planarity plays a key role in our arguments, since there are posets such that (1) dimension is exponential in height and (2) the cover graph excludes K5K_5 as a minor

    It\u27s Time: A Meta-Analysis on the Self-Control-Deviance Link

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    Purpose The current meta-analysis examines the link between self-control and measures of crime and deviance, taking stock of the empirical status of self-control theory and focusing on work published between 2000 and 2010. Methods A total of 796 studies were reviewed for inclusion/exclusion criteria and yielded a final study sample of 99 studies (88 cross-sectional and 19 longitudinal effect sizes, analyzed separately). Random effects mean correlations between self-control and deviance were analyzed for cross-sectional and longitudinal studies, respectively. Publication bias was assessed using multiple methods. Results A random effects mean correlation between self-control and deviance was Mr = 0.415 for cross-sectional studies and Mr = 0.345 for longitudinal ones; this effect did not significantly differ by study design. Studies with more male participants, studies based on older or US-based populations, and self-report studies found weaker effects. Conclusions Substantial empirical support was found for the main argument of self-control theory and on the transdisciplinary link between self-control and measures of crime and deviance. In contrast to Pratt and Cullen, but consistent with theory, the effect from cross-sectional versus longitudinal studies did not significantly differ. There was no evidence of publication bias

    Towards the Development of a Risk Model for Unmanned Vessels Design and Operations

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    An unmanned merchant vessel seems to be escaping from the stage of idea exploration. Once the concept proofs its safety, it may become a part of maritime reality. Although the safety aspect of such a ship has been addressed by a handful of scholars, the problem remains open. This is mainly due to lack of knowledge regarding actual operational circumstances and design of unmanned ships, which are yet to be developed. In the attempt of bridging this gap, the risk analysis associated with unmanned ships needs to be carried out, where all relevant hazards and consequences are assessed and quantified in systematic manner. In this paper we present the results of a first step of such analysis, namely the hazard analysis associated with the unmanned ships. The list of hazards covers various aspects of unmanned shipping originating from both design and operational phases of vessel’s life. Subsequently the hazards and related consequences are organized in a casual manner, resulting in the development of a structure of a risk model

    Bias Reduction for Sum Estimation

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    Einstein-Podolsky-Rosen correlations of Dirac particles - quantum field theory approach

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    We calculate correlation function in the Einstein--Podolsky--Rosen type of experiment with massive relativistic Dirac particles in the framework of the quantum field theory formalism. We perform our calculations for states which are physically interesting and transforms covariantly under the full Lorentz group action, i.e. for pseudoscalar and vector state.Comment: 9 pages, 2 figures. Published versio
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