196 research outputs found
Casimir experiments showing saturation effects
We address several different Casimir experiments where theory and experiment
disagree. First out is the classical Casimir force measurement between two
metal half spaces; here both in the form of the torsion pendulum experiment by
Lamoreaux and in the form of the Casimir pressure measurement between a gold
sphere and a gold plate as performed by Decca et al.; theory predicts a large
negative thermal correction, absent in the high precision experiments. The
third experiment is the measurement of the Casimir force between a metal plate
and a laser irradiated semiconductor membrane as performed by Chen et al.; the
change in force with laser intensity is larger than predicted by theory. The
fourth experiment is the measurement of the Casimir force between an atom and a
wall in the form of the measurement by Obrecht et al. of the change in
oscillation frequency of a 87 Rb Bose-Einstein condensate trapped to a fused
silica wall; the change is smaller than predicted by theory. We show that
saturation effects can explain the discrepancies between theory and experiment
observed in all these cases.Comment: 10 pages, 11 figure
Casimir effects in systems containing 2D layers, like graphene and 2D electron gases
We present a variety of methods to derive the Casimir interaction in planar
systems containing two-dimensional layers. Examples where this can be of use is
graphene, graphene-like layers and two-dimensional electron gases. We present
results for two free standing layers and for one layer above a substrate. The
results can easily be extended to systems with a larger number of layers.Comment: 25 pages, 1 figure, 113 equation
Electromagnetic normal modes and Casimir effects in layered structures
We derive a general procedure for finding the electromagnetic normal modes in
layered structures. We apply this procedure to planar, spherical and
cylindrical structures. These normal modes are important in a variety of
applications. They are the only input needed in calculations of Casimir
interactions. We present explicit expression for the condition for modes and
Casimir energy for a large number of specific geometries. The layers are
allowed to be two-dimensional so graphene and graphene-like sheets as well as
two-dimensional electron gases can be handled within the formalism. Also forces
on atoms in layered structures are obtained. One side-result is the van der
Waals and Casimir-Polder interaction between two atoms.Comment: 50 pages, 21 figures, more than 400 equation
Beyond the simple Proximity Force Approximation: geometrical effects on the non-retarded Casimir interaction
We study the geometrical corrections to the simple Proximity Force
Approximation for the non-retarded Casimir force. We present analytical results
for the force between objects of various shapes and substrates, and between
pairs of objects. We compare the results to those from more exact numerical
calculations. We treat spheres, spheroids, cylinders, cubes, cones, and wings;
the analytical PFA results together with the geometrical correction factors are
summarized in a table.Comment: 18 pages, 19 figures, 1 tabl
Numerical study of the effect of structure and geometry on van der Waals forces
We use multipolar expansions to find the force on a gold coated sphere above
a gold substrate; we study both an empty gold shell and a gold coated
polystyrene sphere. We find four characteristic separation ranges. In the first
region, which for the empty gold shell occurs for distances, d, smaller than
the thickness of the coating, the result agrees with that on a solid gold
sphere and varies as d^(-2); for larger separations there is a region where the
force behaves as if the coating is strictly two dimensional and varies as
d^(-5/2); in the third region the dependence is more unspecific; in the forth
region when d is larger than the radius, the force varies as d^(-4). For
homogeneous objects of more general shapes we introduce a numerical method
based on the solution of an integral equation for the electric field over a
system of objects with arbitrary shapes. We study the effect of shape and
orientation on the van der Waals interaction between an object and a substrate
and between two objects.Comment: 8 pages, presented in the QFEXT07 conference, submitted to Journal of
Physics
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