2,568 research outputs found
1/t pressure and fermion behaviour of water in two dimensions
A variety of metal vacuum systems display the celebrated 1/t pressure, namely
power-law dependence on time t, with the exponent close to unity, the origin of
which has been a long-standing controversy. Here we propose a chemisorption
model for water adsorbates, based on the argument for fermion behaviour of
water vapour adsorbed on a stainless-steel surface, and obtain analytically the
power-law behaviour of pressure, with an exponent of unity. Further, the model
predicts that the pressure should depend on the temperature T according to
T^(3/2), which is indeed confirmed by our experiment. Our results should help
elucidate the unique characteristics of the adsorbed water.Comment: 11 pages, 4 figure
Random walk approach to the d-dimensional disordered Lorentz gas
A correlated random walk approach to diffusion is applied to the disordered
nonoverlapping Lorentz gas. By invoking the Lu-Torquato theory for chord-length
distributions in random media [J. Chem. Phys. 98, 6472 (1993)], an analytic
expression for the diffusion constant in arbitrary number of dimensions d is
obtained. The result corresponds to an Enskog-like correction to the Boltzmann
prediction, being exact in the dilute limit, and better or nearly exact in
comparison to renormalized kinetic theory predictions for all allowed densities
in d=2,3. Extensive numerical simulations were also performed to elucidate the
role of the approximations involved.Comment: 5 pages, 5 figure
On anomalous diffusion in a plasma in velocity space
The problem of anomalous diffusion in momentum space is considered for
plasma-like systems on the basis of a new collision integral, which is
appropriate for consideration of the probability transition function (PTF) with
long tails in momentum space. The generalized Fokker-Planck equation for
description of diffusion (in momentum space) of particles (ions, grains etc.)
in a stochastic system of light particles (electrons, or electrons and ions,
respectively) is applied to the evolution of the momentum particle distribution
in a plasma. In a plasma the developed approach is also applicable to the
diffusion of particles with an arbitrary mass relation, due to the small
characteristic momentum transfer. The cases of an exponentially decreasing in
momentum space (including the Boltzmann-like) kernel in the PT-function, as
well as the more general kernels, which create the anomalous diffusion in
velocity space due to the long tail in the PT-function, are considered.
Effective friction and diffusion coefficients for plasma-like systems are
found.Comment: 18 pages, no figure
Inhomogeneity of dusty crystals and plasma diagnostics
Real dusty crystals are inhomogeneous due to the presence of external forces. We suggest approximations for calculations of different types of inhomogeneous DC (chain and DC with a few slabs) in the equilibrium state. The results are in a good agreement with experimental results and can be used as an effective diagnostic method for many dusty systems
It is Hobbes, not Rousseau:an experiment on voting and redistribution
We perform an experiment which provides a laboratory replica of some
important features of the welfare state. In the experiment, all individuals in a group
decide whether to make a costly effort, which produces a random (independent) outcome
for each one of them. The group members then vote on whether to redistribute
the resulting and commonly known total sum of earnings equally amongst themselves.
This game has two equilibria, if played once. In one of them, all players make
effort and there is little redistribution. In the other one, there is no effort and nothingWe thank Iris Bohnet, Tim Cason, David Cooper, John Duffy, Maia Guell, John Van Huyck and Robin Mason for helpful conversations and encouragement. The comments of the Editor and two referees helped improve the paper. We gratefully acknowledge the financial support from Spain’s Ministry of Science and Innovation under grants CONSOLIDER INGENIO 2010 CSD2006-0016 (all authors), ECO2009-10531 (Cabrales), ECO2008-01768 (Nagel) and the Comunidad de Madrid under grant Excelecon (Cabrales), the Generalitat de Catalunya and the CREA program (Nagel), and project SEJ2007-64340 of Spain’s Ministerio de Educación y Ciencia (Rodríguez Mora).Publicad
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