4,547 research outputs found

    A first look at maximally twisted mass lattice QCD calculations at the physical point

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    In this contribution, a first look at simulations using maximally twisted mass Wilson fermions at the physical point is presented. A lattice action including clover and twisted mass terms is presented and the Monte Carlo histories of one run with two mass-degenerate flavours at a single lattice spacing are shown. Measurements from the light and heavy-light pseudoscalar sectors are compared to previous Nf=2N_f = 2 results and their phenomenological values. Finally, the strategy for extending simulations to Nf=2+1+1N_f = 2 + 1 + 1 is outlined.Comment: presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

    A Rigourous Treatment of the Lattice Renormalization Problem of F_B

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    The BB-meson decay constant can be measured on the lattice using a 1/mb1/m_b expansion. To relate the physical quantity to Monte Carlo data one has to know the renormalization coefficient, ZZ, between the lattice operators and their continuum counterparts. We come back to this computation to resolve discrepancies found in previous calculations. We define and discuss in detail the renormalization procedure that allows the (perturbative) computation of ZZ. Comparing the one-loop calculations in the effective Lagrangian approach with the direct two-loop calculation of the two-point BB-meson correlator in the limit of large bb-quark mass, we prove that the two schemes give consistent results to order Îąs\alpha_s. We show that there is, however, a renormalization prescription ambiguity that can have sizeable numerical consequences. This ambiguity can be resolved in the framework of an O(a)O(a) improved calculation, and we describe the correct prescription in that case. Finally we give the numerical values of ZZ that correspond to the different types of lattice approximations discussed in the paper.Comment: 27 pages, 2 figures (Plain TeX, figures in an appended postscript file

    American color science, 1831-1931

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    Thesis (Ph. D. in History, Anthropology, and Science, Technology and Society (HASTS))--Massachusetts Institute of Technology, Program in Science, Technology and Society, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 365-389).Although vision was seldom studied in Antebellum America, color and color perception became a critical field of scientific inquiry in the United States during the Gilded Age and progressive era. Through a historical investigation of color science in the United States in the late nineteenth and early twentieth centuries, I argue that attempts to scientifically measure, define, and regulate color were part of a wider program to construct a more rational, harmonious, and efficient American polity starting from one of the very baseline perceptual components of reality - the experience of color. As part of this program, I argue secondly that color science was as much a matter of prescription as description - that is, color scientists didn't simply endeavor to reveal the facts of perception and apply them to social problems, they wanted to train everyday citizens to see scientifically, and thereby create citizens whose eyes, bodies, and minds were both medically healthy and morally tuned to the needs of the modern American nation. Finally, I argue not simply that perception has a history - i.e. that perceptual practices change over time, and that, for Americans of a century ago, experiences of color sensations were not taken as given but had to be laboriously crafted - but also that this history weighs heavily upon our present day understanding of visual reality, as manifested not least of all in scientific studies of vision, language, and cognition. Employing a close reading of the archival and published sources of a range of actors including physicist Ogden Rood, semiotician Charles Peirce, logician Christine Ladd-Franklin, board game magnate Milton Bradley, and art professor Alfred Munsell, among others, this study reveals the origins of some of the most deeply-rooted conceptions of color in modern American culture.by Michael Paul Rossi.Ph.D.in History, Anthropology, and Science, Technology and Society (HAST

    Who wants to move? The role of neighbourhood change

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    This is the author accepted manuscript. The final version is available from SAGE via http://dx.doi.org/10.1177/0308518X15615367 There is growing interest in how, when and where neighbourhoods affect individual behaviours and outcomes. In Britain, falling levels of owner-occupation and the growth of ethnic minority populations have sparked a debate about how neighbourhood characteristics and neighbourhood change intersect with the decision to move. In this paper we investigate how mobility preferences vary with neighbourhood characteristics and neighbourhood change. We use multilevel logistic regression models to test whether this is configured by personal attributes or attachment to one's neighbourhood and perceived similarity to one's neighbours. The results show that neighbourhood deprivation, changes in neighbourhood ethnic composition and changes in tenure mix are associated with preferring to move. Importantly, we show that a feeling of belonging to the neighbourhood or feeling similar to others in the neighbourhood significantly reduces the desire to move. </jats:p

    Vortex waistlines and long range fluctuations

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    We examine the manner in which a linear potential results from fluctuations due to vortices linked with the Wilson loop. Our discussion is based on exact relations and inequalities between the Wilson loop and the vortex and electric flux order parameters. We show that, contrary to the customary naive picture, only vortex fluctuations of thickness of the order of the spatial linear size of the loop are capable of producing a strictly linear potential. An effective theory of these long range fluctuations emerges naturally in the form of a strongly coupled Z(N) lattice gauge theory. We also point out that dynamical fermions introduced in this medium undergo chiral symmetry breaking.Comment: 17 pages, LaTex file with 7 eps figures, revised references, minor comments adde

    New mobilities across the lifecourse: A framework for analysing demographically-linked drivers of migration

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    Date of acceptance: 17/02/2015Taking the life course as the central concern, the authors set out a conceptual framework and define some key research questions for a programme of research that explores how the linked lives of mobile people are situated in time–space within the economic, social, and cultural structures of contemporary society. Drawing on methodologically innovative techniques, these perspectives can offer new insights into the changing nature and meanings of migration across the life course.Publisher PDFPeer reviewe

    Cr/Sc multilayer radiator for parametric EUV radiation in "water-window" spectral range

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    The results of experimental investigation of parametric radiation generated by 5.7 MeV electrons in a multilayer structure consisting of 100 Cr/Sc bi-layers deposited on a Si[3]N[4] membrane are presented. The multilayer structure was specially created for generation of parametric radiation with photon energy in "water-window" spectral range. First test measurements of angular distributions of radiation have been done and discussed

    The Messenger Sector of SUSY Flavour Models and Radiative Breaking of Flavour Universality

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    The flavour messenger sectors and their impact on the soft SUSY breaking terms are investigated in SUSY flavour models. In the case when the flavour scale M is below the SUSY breaking mediation scale M_S, the universality of soft terms, even if assumed at M_S, is radiatively broken. We estimate this effect in a broad class of models. In the CKM basis that effect gives flavour off-diagonal soft masses comparable to the tree-level estimate based on the flavour symmetry.Comment: 24 pages, 3 figures. v3: minor changes in the text, typos corrected, version accepted for publication in JHE
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