11 research outputs found
Material Dependence of the Wire-Particle Casimir Interaction
We study the Casimir interaction between a metallic cylindrical wire and a
metallic spherical particle by employing the scattering formalism. At large
separations, we derive the asymptotic form of the interaction. In addition, we
find the interaction between a metallic wire and an isotropic atom, both in the
non-retarded and retarded limits. We identify the conditions under which the
asymptotic Casimir interaction does not depend on the material properties of
the metallic wire and the particle. Moreover, we compute the exact Casimir
interaction between the particle and the wire numerically. We show that there
is a complete agreement between the numerics and the asymptotic energies at
large separations. For short separations, our numerical results show good
agreement with the proximity force approximation
Universality versus material dependence of fluctuation forces between metallic wires
We calculate the Casimir interaction between two parallel wires and between a
wire and a metall plate. The dielectric properties of the objects are described
by the plasma, Drude and perfect metal models. We find that at asymptotically
large separation interactions involving plasma wires and/or plates are
independent of the material properties, but depend on the dc conductivity
for Drude wires. Counterintuitively, at intermediate separations the
interaction involving Drude wires can become independent of . At
smaller separations, we compute the interaction numerically and observe an
approach to the proximity approximation
Collective charge fluctuations and Casimir interactions for quasi one-dimensional metals
We investigate the Casimir interaction between two parallel metallic
cylinders and between a metallic cylinder and plate. The material properties of
the metallic objects are implemented by the plasma, Drude and perfect metal
model dielectric functions. We calculate the Casimir interaction numerically at
all separation distances and analytically at large separations. The
large-distance asymptotic interaction between one plasma cylinder parallel to
another plasma cylinder or plate does not depend on the material properties,
but for a Drude cylinder it depends on the dc conductivity . At
intermediate separations, for plasma cylinders the asymptotic interaction
depends on the plasma wave length while for Drude cylinders
the Casimir interaction can become independent of the material properties. We
confirm the analytical results by the numerics and show that at short
separations, the numerical results approach the proximity force approximation
Ellipsoidal particles at fluid interfaces
For partially wetting, ellipsoidal colloids trapped at a fluid interface,
their effective, interface--mediated interactions of capillary and
fluctuation--induced type are analyzed. For contact angles different from
90, static interface deformations arise which lead to anisotropic capillary
forces that are substantial already for micrometer--sized particles. The
capillary problem is solved using an efficient perturbative treatment which
allows a fast determination of the capillary interaction for all distances
between and orientations of two particles. Besides static capillary forces,
fluctuation--induced forces caused by thermally excited capillary waves arise
at fluid interfaces. For the specific choice of a spatially fixed three--phase
contact line, the asymptotic behavior of the fluctuation--induced force is
determined analytically for both the close--distance and the long--distance
regime and compared to numerical solutions.Comment: 10 pages, submitted to EPJE (Special Issue Soft Matter Conference
Aachen'07
Membrane-mediated interactions
Interactions mediated by the cell membrane between inclusions, such as
membrane proteins or antimicrobial peptides, play important roles in their
biological activity. They also constitute a fascinating challenge for
physicists, since they test the boundaries of our understanding of
self-assembled lipid membranes, which are remarkable examples of
two-dimensional complex fluids. Inclusions can couple to various degrees of
freedom of the membrane, resulting in different types of interactions. In this
chapter, we review the membrane-mediated interactions that arise from direct
constraints imposed by inclusions on the shape of the membrane. These effects
are generic and do not depend on specific chemical interactions. Hence, they
can be studied using coarse-grained soft matter descriptions. We deal with
long-range membrane-mediated interactions due to the constraints imposed by
inclusions on membrane curvature and on its fluctuations. We also discuss the
shorter-range interactions that arise from the constraints on membrane
thickness imposed by inclusions presenting a hydrophobic mismatch with the
membrane.Comment: 38 pages, 10 figures, pre-submission version. In: Bassereau P., Sens
P. (eds) Physics of Biological Membranes. Springer, Cha