8,957 research outputs found

    Towards a framework for analyzing interactions between social science and environmental policy

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    Interactions between social science and environmental policy have become increasingly important over the past 25 years. There has, however, been little analysis of the roles that social scientists adopt and the contributions they make. In this paper we begin the process, offering tentative answers to two key questions: in relation to environmental problems: (1) how do social science and public policy interact? and (2) in the future, what types of interactions can social scientists engage in? To answer these questions we build on research in policy studies and science and technology studies, and extend it through public scholarship debates

    Two Parameters for Three Dimensional Wetting Transitions

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    Critical effects at complete and critical wetting in three dimensions are studied using a coupled effective Hamiltonian H[s(y),\ell]. The model is constructed via a novel variational principle which ensures that the choice of collective coordinate s(y) near the wall is optimal. We highlight the importance of a new wetting parameter \Omega(T) which has a strong influence on critical properties and allows the status of long-standing Monte-Carlo simulation controversies to be re-examined.Comment: 4 pages RevTex, 2 encapsulated postscript figures, to appear in Europhys. Let

    Correlation function algebra for inhomogeneous fluids

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    We consider variational (density functional) models of fluids confined in parallel-plate geometries (with walls situated in the planes z=0 and z=L respectively) and focus on the structure of the pair correlation function G(r_1,r_2). We show that for local variational models there exist two non-trivial identities relating both the transverse Fourier transform G(z_\mu, z_\nu;q) and the zeroth moment G_0(z_\mu,z_\nu) at different positions z_1, z_2 and z_3. These relations form an algebra which severely restricts the possible form of the function G_0(z_\mu,z_\nu). For the common situations in which the equilibrium one-body (magnetization/number density) profile m_0(z) exhibits an odd or even reflection symmetry in the z=L/2 plane the algebra simplifies considerably and is used to relate the correlation function to the finite-size excess free-energy \gamma(L). We rederive non-trivial scaling expressions for the finite-size contribution to the free-energy at bulk criticality and for systems where large scale interfacial fluctuations are present. Extensions to non-planar geometries are also considered.Comment: 15 pages, RevTex, 4 eps figures. To appear in J.Phys.Condens.Matte

    Monte Carlo simulation of a two-field effective Hamiltonian of complete wetting

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    Recent work on the complete wetting transition for three dimensional systems with short-ranged forces has emphasized the role played by the coupling of order-parameter fluctuations near the wall and depinning interface. It has been proposed that an effective two-field Hamiltonian, which predicts a renormalisation of the wetting parameter, could explain the controversy between RG analysis of the capillary-wave model and Monte Carlo simulations on the Ising model. In this letter results of extensive Monte Carlo simulations of the two-field model are presented. The results are in agreement with prediction of a renormalized wetting parameter ω\omega .Comment: To appear in Europhysics Letters. Latex file, 6 pages, 2 figure

    Coupled Fluctuations near Critical Wetting

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    Recent work on the complete wetting transition has emphasized the role played by the coupling of fluctuations of the order parameter at the wall and at the depinning fluid interface. Extending this approach to the wetting transition itself we predict a novel crossover effect associated with the decoupling of fluctuations as the temperature is lowered towards the transition temperature T_W. Using this we are able to reanalyse recent Monte-Carlo simulation studies and extract a value \omega(T_W)=0.8 at T_W=0.9T_C in very good agreement with long standing theoretical predictions.Comment: 4 pages, LaTex, 1 postscript figur

    Fluid adsorption near an apex: Covariance between complete and critical wetting

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    Critical wetting is an elusive phenomenon for solid-fluid interfaces. Using interfacial models we show that the diverging length scales, which characterize complete wetting at an apex, precisely mimic critical wetting with the apex angle behaving as the contact angle. Transfer matrix, renormalization group (RG) and mean field analysis (MF) shows this covariance is obeyed in 2D, 3D and for long and short ranged forces. This connection should be experimentally accesible and provides a means of checking theoretical predictions for critical wetting.Comment: 4 pages, 1 figure, submitted to Physical Review Letter

    Brane Gas Inflation

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    We consider the brane gas picture of the early universe. At later stages, when there are no winding modes and the background is free to expand, we show that a moving 3-brane, which we identify with our universe, can inflate even though it is radiation-dominated. The crucial ingredients for successful inflation are the coupling to the dilaton and the equation of state of the bulk. If we suppose the brane initially forms in a collision of higher-dimensional branes, then the spectrum of primordial density fluctuations naturally has a thermal origin.Comment: 4 pages, 1 figur
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