4,586 research outputs found

    Arguments in a Sartorial Mode, or the Asymmetries of History and Philosophy of Science

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    History of science and philosophy of science are not perfectly complementary disciplines. Several important asymmetries govern their relationship. These asymmetries, concerning levels of analysis, evidence, theories, writing, and training show that to be a decent philosopher of science is more difficult than being a decent historian. But to be a good historian-well, the degree of difficulty is reversed

    Charmonium excited state spectrum in lattice QCD

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    Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.Comment: Fixed typos: normalisation of chi-squared, some operator projections in appendix, missing lattice irrep tabl

    Impacts of climate change in coastal systems in Europe. PESETA-Coastal Systems study

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    Results of the physical impacts and adaptation cost assessment of sea-level rise for the European Union are presented for the A2 and B2 SRES socio-economic storylines and for a range of plausible sea-level rise scenarios, using data from the ECHAM4 and HADCM3 Global Climate Models (GCMs) models. In addition, to better understand the sensitivity of the results to the magnitude of sea-level rise, the full IPCC (2001) range of sea level rise predictions and scenarios of no climate change have also been modelled. These results are all derived using the global Dynamic Interactive Vulnerability Assessment (DIVA) tool for assessing regional to global coastal impacts and adaptation. Both the physical and economic impacts of sea-level rise increase with time for both the A2 and B2 storylines, especially under scenarios of high sea-level rise. Without adaptation, significant impacts and therefore damages are apparent. Significant populations are threatened with displacement by flooding and coastal erosion. An exploratory adaptation analysis using standard protection measures of dike construction and beach nourishment, where benefit-cost analysis suggests this is the optimum response, reduces these impacts significantly. While adaptation in Europe is likely to be much more diverse than these two smple options, these results demonstrate the significant benefits of protection, and more generally suggest that widespread adaptation to sustain human coastal activities would be prudent. Moreover, under these protection assumptions, coastal ecosystems are significantly reduced in area, especially under the high sea-level rise scenario and climate change raises significant challenges for wider coastal management in Europe, even if human uses in the coastal zone are protected.JRC.DG.J.2-The economics of climate change, energy and transpor

    Excited state baryon spectroscopy from lattice QCD

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    We present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including J = 7/2, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of SU(6) x O(3) representations and a counting of levels that is consistent with the non-relativistic qqqqqq constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.Comment: 29 pages, 18 figure

    Clustering Analyses of 300,000 Photometrically Classified Quasars--II. The Excess on Very Small Scales

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    We study quasar clustering on small scales, modeling clustering amplitudes using halo-driven dark matter descriptions. From 91 pairs on scales <35 kpc/h, we detect only a slight excess in quasar clustering over our best-fit large-scale model. Integrated across all redshifts, the implied quasar bias is b_Q = 4.21+/-0.98 (b_Q = 3.93+/-0.71) at ~18 kpc/h (~28 kpc/h). Our best-fit (real-space) power index is ~-2 (i.e., ξ(r)r2\xi(r) \propto r^{-2}), implying steeper halo profiles than currently found in simulations. Alternatively, quasar binaries with separation <35 kpc/h may trace merging galaxies, with typical dynamical merger times t_d~(610+/-260)m^{-1/2} Myr/h, for quasars of host halo mass m x 10^{12} Msolar/h. We find UVX quasars at ~28 kpc/h cluster >5 times higher at z > 2, than at z < 2, at the 2.0σ2.0\sigma level. However, as the space density of quasars declines as z increases, an excess of quasar binaries (over expectation) at z > 2 could be consistent with reduced merger rates at z > 2 for the galaxies forming UVX quasars. Comparing our clustering at ~28 kpc/h to a \xi(r)=(r/4.8\Mpch)^{-1.53} power-law, we find an upper limit on any excess of a factor of 4.3+/-1.3, which, noting some caveats, differs from large excesses recently measured for binary quasars, at 2.2σ2.2\sigma. We speculate that binary quasar surveys that are biased to z > 2 may find inflated clustering excesses when compared to models fit at z < 2. We provide details of 111 photometrically classified quasar pairs with separations <0.1'. Spectroscopy of these pairs could significantly constrain quasar dynamics in merging galaxies.Comment: 12pages, 3 figures, 2 tables; uses amulateapj; accepted to Ap

    Virtual Colonoscopy

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    Industrial structural geology : principles, techniques and integration : an introduction

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    The authors wish to acknowledge the generous financial support provided in association with this volume to the Geological Society and the Petroleum Group by Badley Geoscience Ltd, BP, CGG Robertson, Dana Petroleum Ltd, Getech Group plc, Maersk Oil North Sea UK Ltd, Midland Valley Exploration Ltd, Rock Deformation Research (Schlumberger) and Borehole Image & Core Specialists (Wildcat Geoscience, Walker Geoscience and Prolog Geoscience). We would like to thank the fine team at the Geological Society’s Publishing House for the excellent support and encouragement that they have provided to the editors and authors of this Special Publication.Peer reviewedPublisher PD

    Isoscalar meson spectroscopy from lattice QCD

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    We extract to high statistical precision an excited spectrum of single-particle isoscalar mesons using lattice QCD, including states of high spin and, for the first time, light exotic JPC isoscalars. The use of a novel quark field construction has enabled us to overcome the long-standing challenge of efficiently including quark-annihilation contributions. Hidden-flavor mixing angles are extracted and while most states are found to be close to ideally flavor mixed, there are examples of large mixing in the pseudoscalar and axial sectors in line with experiment. The exotic JPC isoscalar states appear at a mass scale comparable to the exotic isovector states.Comment: 4 pages, 4 figure
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