1,082 research outputs found
Simulating Van der Waals-interactions in water/hydrocarbon-based complex fluids
In systems composed of water and hydrocarbons Van der Waals-interactions are
dominated by the non-retarded, classical (Keesom) part of the
Lifshitz-interaction; the interaction is screened by salt and extends over
mesoscopic distances of the order of the size of the (micellar) constituents of
complex fluids. We show that these interactions are included intrinsically in a
recently introduced local Monte Carlo algorithm for simulating electrostatic
interactions between charges in the presence of non-homogeneous dielectric
media
A fluctuation-corrected functional of convex Poisson–Boltzmann theory
International audiencePoisson-Boltzmann theory allows to study soft matter and biophysical systems involving point-like charges of low valencies. The inclusion of fluctuation corrections beyond the mean-field approach typically requires the application of loop expansions around a mean-field solution for the electrostatic potential φ(r), or sophisticated variational approaches. Recently, Poisson-Boltzmann theory has been recast, via a Legendre transform, as a mean-field theory involving the dielectric displacement field D(r). In this paper we consider the path integral formulation of this dual theory. Exploiting the transformation between φ and D, we formulate a dual Sine-Gordon field theory in terms of the displacement field and provide a strategy for precise numerical computations of free energies beyond the leading order
Electrostatic interactions in the presence of surface charge regulation: exact results
We study the problem of charge regulation and its effects on electrostatic
interactions between dissociable charge groups immersed in a univalent
electrolyte, within a family of one dimensional exactly solvable models. We
consider the case of both charge regulated plates, but also the interaction of
pairs of finite size dielectric "particles". Using the transfer matrix
formalism we are able to determine the disjoining pressure as well as the
correlations between the charge and the dipole moments of the objects as a
function of their separation and electrolyte concentrationComment: 6 pages, 3 figure
Simulating nanoscale dielectric response
We introduce a constrained energy functional to describe dielectric response.
We demonstrate that the local functional is a generalization of the long ranged
Marcus energy. Our re-formulation is used to implement a cluster Monte Carlo
algorithm for the simulation of dielectric media. The algorithm avoids solving
the Poisson equation and remains efficient in the presence of spatial
heterogeneity, nonlinearity and scale dependent dielectric properties.Comment: 4 pages, 2 figures. Revtex
Comment on "Elasticity Model of a Supercoiled DNA Molecule"
We perform simulations to numerically study the writhe distribution of a
stiff polymer. We compare with analytic results of Bouchiat and Mezard (PRL 80
1556- (1998); cond-mat/9706050).Comment: 1 page, 1 figure revtex
Probability distribution of the maximum of a smooth temporal signal
We present an approximate calculation for the distribution of the maximum of
a smooth stationary temporal signal X(t). As an application, we compute the
persistence exponent associated to the probability that the process remains
below a non-zero level M. When X(t) is a Gaussian process, our results are
expressed explicitly in terms of the two-time correlation function,
f(t)=.Comment: Final version (1 major typo corrected; better introduction). Accepted
in Phys. Rev. Let
Simulation of a semiflexible polymer in a narrow cylindrical pore
The probability that a randomly accelerated particle in two dimensions has
not yet left a simply connected domain after a time decays as
for long times. The same quantity also determines the
confinement free energy per unit length of a
semiflexible polymer in a narrow cylindrical pore with cross section . From simulations of a randomly accelerated particle we estimate the
universal amplitude of for both circular and rectangular cross
sections.Comment: 10 pages, 2 eps figure
Elastic fluctuations as observed in a confocal slice
Recent confocal experiments on colloidal solids motivate a fuller study of
the projection of three-dimensional fluctuations onto a two-dimensional
confocal slice. We show that the effective theory of a projected crystal
displays several exceptional features, such as non-standard exponents in the
dispersion relations. We provide analytic expressions for the effective
two-dimensional elastic properties which allow one to work back from sliced
experimental observations to three-dimensional elastic constants.Comment: 5 pages, 2 figure
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