27,294 research outputs found

    Ramsauer approach for light scattering on non-absorbing spherical particles and application to the Henyey-Greenstein phase function

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    We present a new method to study light scattering on non-absorbing spherical particles. This method is based on the Ramsauer approach, a model known in atomic an nuclear physics. Its main advantage is its intuitive understanding of the underlying physics phenomena. We show that although the approximations are numerous, the Ramsauer analytical solutions describe fairly well the scattering phase function and the total cross section. Then this model is applied to the Henyey-Greenstein parameterisation of scattering phase function to give a relation between its asymmetry parameter and the mean particle size.Comment: 25 pages, 12 figures, journal paper, accepted in Applied Optics. arXiv admin note: text overlap with arXiv:0903.297

    BEC-BCS Crossover in Neutron Matter with Renormalization Group based Effective Interactions

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    We study pure neutron matter in the BEC-BCS crossover regime using renormalization group based low-momentum interactions within the Nozi\`eres-Schmitt-Rink framework. This is an attempt to go beyond the mean field description for low-density matter. We work in the basis of so-called Weinberg eigenvectors where the operator G0VG_0V is diagonal, which proves to be an excellent choice that allows one to use non-local interactions in a very convenient way. We study the importance of correlations as a function of density. We notice that there is a significant reduction of the BCS critical temperature at low-densities as the neutron matter approaches the unitary limit.Comment: 10 pages and 8 figures, Figs 6 and 7 now includes higher cut-offs, discussion of the cut-off dependence improved, new Summary and Outlook section and new references adde

    On the hierarchy of neutrino masses

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    We present a model of neutrino masses combining the seesaw mechanism and strong Dirac mass hierarchy and at the same time exhibiting a significantly reduced hierarchy at the level of active neutrino masses. The heavy Majorana masses are assumed to be degenerate. The suppression of the hierarchy is due to a symmetric and unitary operator R whose role is discussed. The model gives realistic mixing and mass spectrum. The mixing of atmospheric neutrinos is attributed to the charged lepton sector whereas the mixing of solar neutrinos is due to the neutrino sector. Small U_e3 is a consequence of the model. The masses of the active neutrinos are given by μ3Δm@2\mu_3\approx\sqrt{\Delta m_{@}^2} and μ1/μ2tan2θ\mu_1/\mu_2\approx \tan^2\theta_\odot.Comment: 12 pages; Talk presented by M. Jezabek at 'Supersymmetry and Brane Worlds,' Fifth European Meeting Planck 02, Kazimierz, Poland, May 25-29, 2002, to appear in Acta Phys. Polon.

    Discussion of: A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?

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    Discussion of "A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?" by B.B. McShane and A.J. Wyner [arXiv:1104.4002]Comment: Published in at http://dx.doi.org/10.1214/10-AOAS398G the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Momentum Dependence of the Pion Cloud for Rho Mesons in Nuclear Matter

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    We extend hadronic models for rho-meson propagation in cold nuclear matter via coupling to in-medium pions to include finite three-momentum. Special care is taken to preserve gauge invariance. Consequences for photoabsorption on the proton and on nuclei as well as for the dilepton production in relativistic heavy-ion collisions are discussed.Comment: 32 pages, 18 figures. Corrected version, accepted for publication in Nucl. Phys.

    A Microscopic Calculation of Photoabsorption Cross Sections on Protons and Nuclei

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    A recently developed model for ρ\rho-meson propagation in dense hadronic matter is applied to total photoabsorption cross sections in γ\gamma-proton and γ\gamma-nucleus reactions. Within the vector dominance model the photon coupling to the virtual pion cloud of the nucleon, two-body meson-exchange currents, as well as γ\gamma-nucleon resonances are included. Whereas the γp\gamma p reaction is determined by the low-density limit of the model, higher orders in the nuclear density are important to correctly account for the experimental spectra observed on both light and heavy nuclei over a wide range of photon energies, including the region below the pion threshold. In connection with soft dilepton spectra in high-energy heavy-ion collisions we emphasize the importance of photoabsorption to further constrain the parameters of the model.Comment: 10 pages RevTeX, 2 eps-figure

    Foreign Takeovers and Wage Dispersion in Hungary

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    This study tests FDI technology spillover models with the assumption that learning takes time against wage bargaining models by estimating the wage-premium of a foreign takeover. The technology spillover theory predicts a larger wage growth in firms taken over by foreign investors than in local firms. However, this wage growth should be confined to high-skilled workers or workers with a high level of education. Wage bargaining models also predict such a wage growth. But it should be confined to workers who are organized in trade unions, i.e. workers with low or medium level of education or skill. We apply Hungarian employee-employer matched data from 1992 until 2001, and reject the FDI technology spillover model in favor of the wage bargaining model when differentiating the wage premium by education or occupation, both by applying Mincer wage regressions and the nearest-neighbor matching method.FDI, foreign takeover, cross-border M&A, Mincer wage regression, employee-employer matched data, nearest-neighbor matching

    Quantum fluids in nanopores

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    We describe calculations of the properties of quantum fluids inside nanotubes of various sizes. Very small radius (RR) pores confine the gases to a line, so that a one-dimensional (1D) approximation is applicable; the low temperature behavior of 1D 4^4He is discussed. Somewhat larger pores permit the particles to move off axis, resulting eventually in a transition to a cylindrical shell phase--a thin film near the tube wall; we explored this behavior for H2_2. At even larger R1R\sim 1 nm, both the shell phase and an axial phase are present. Results showing strong binding of cylindrical liquids 4^4He and 3^3He are discussed.Comment: 8 pages, 4 figures, uses ws-ijmpb, graphicx, xspace; minor revisions from version published in Proc. 13th Intl. Conference on Recent Progress in Many-Body Theories (QMBT13), Buenos Aires, 200

    Variation aware analysis of bridging fault testing

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    This paper investigates the impact of process variation on test quality with regard to resistive bridging faults. The input logic threshold voltage and gate drive strength parameters are analyzed regarding their process variation induced influence on test quality. The impact of process variation on test quality is studied in terms of test escapes and measured by a robustness metric. It is shown that some bridges are sensitive to process variation in terms of logic behavior, but such variation does not necessarily compromise test quality if the test has high robustness. Experimental results of Monte-Carlo simulation based on recent process variation statistics are presented for ISCAS85 and -89 benchmark circuits, using a 45nm gate library and realistic bridges. The results show that tests generated without consideration of process variation are inadequate in terms of test quality, particularly for small test sets. On the other hand, larger test sets detect more of the logic faults introduced by process variation and have higher test quality

    Are Cardiovascular Diseases Bad for Economic Growth?

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    We assess the impact of cardiovascular disease (CVD) mortality on economic growth, using a dynamic panel growth regression framework taking into account potential endogeneity problems. We start from a worldwide sample of countries for which data was available and detect a non-linearity in the influence of working age CVD mortality rates on growth across the per capita income scale. We then split the sample (according to the resulting income threshold) into low- and middle-income countries on one hand, and high-income countries on the other hand. In the latter sample we find a robust negative contribution of increasing CVD mortality rates on subsequent five-year growth rates. Not too surprisingly, we find no significant impact in the low- and middle-income country sample.cardiovascular disease, growth empirics, dynamic panel data estimator
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