8,957 research outputs found
Towards a framework for analyzing interactions between social science and environmental policy
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
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
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
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 .Comment: To appear in Europhysics Letters. Latex file, 6 pages, 2 figure
Coupled Fluctuations near Critical Wetting
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
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
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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