37 research outputs found
Improved Effective Range Expansion for Casimir-Polder potential
We study the effective range expansion of scattering on a real Casimir-Polder
potential. We use Liouville transformations which transform the potential
landscape while preserving the reflection and transmission amplitudes. We
decompose the scattering calculation in two more elementary problems, one for
the homogeneous 1/z^4 potential and the other one for the correction to this
idealization. We use the symmetries of the transformed problem and the
properties of the scattering matrices to derive an improved effective range
expansion leading to a more accurate expansion of scattering amplitudes at low
energy
Fluctuations of the Casimir potential above a disordered medium
We study the statistical fluctuations of the Casimir potential felt by an
atom approaching a dielectric disordered medium. Starting from a microscopic
model for the disorder, we calculate the variance of potential fluctuations in
the limit of a weak density of heterogeneities. We show that fluctuations are
essentially governed by scattering of the radiation on a single heterogeneity,
and discuss in which limits they become larger than the average value predicted
by effective medium theory. Finally, for denser disorder we show that multiple
scattering processes become relevant.Comment: 9 pages, 5 figure
Statistical approach to Casimir-Polder potentials in heterogeneous media
We explore the statistical properties of the Casimir-Polder potential between
a dielectric sphere and a three-dimensional heterogeneous medium, by means of
extensive numerical simulations based on the scattering theory of Casimir
forces. The simulations allow us to confirm recent predictions for the mean and
standard deviation of the Casimir potential, and give us access to its full
distribution function in the limit of a dilute distribution of heterogeneities.
These predictions are compared with a simple statistical model based on a
pairwise summation of the individual contributions of the constituting elements
of the medium.Comment: 8 pages, 8 figure
Quantum Reflection of Antihydrogen in the GBAR Experiment
In the GBAR experiment, cold antihydrogen atoms will be left to fall on an
annihilation plate with the aim of measuring the gravitational acceleration of
antimatter. Here, we study the quantum reflection of these antiatoms due to the
Casimir-Polder potential above the plate. We give realistic estimates of the
potential and quantum reflection amplitudes, taking into account the
specificities of antihydrogen and the optical properties of the plate. We find
that quantum reflection is enhanced for weaker potentials, for example above
thin slabs, graphene and nanoporous media.Comment: Workshop on Antimatter and Gravity Bern 2013 Proceeding
The Casimir effect in the sphere-plane geometry
We present calculations of the Casimir interaction between a sphere and a
plane, using a multipolar expansion of the scattering formula. This
configuration enables us to study the nontrivial dependence of the Casimir
force on the geometry, and its correlations with the effects of imperfect
reflection and temperature. The accuracy of the Proximity Force Approximation
(PFA) is assessed, and is shown to be affected by imperfect reflexion. Our
analytical and numerical results at ambient temperature show a rich variety of
interplays between the effects of curvature, temperature, finite conductivity,
and dissipation.Comment: Proceedings of the 10th International Conference "Quantum Field
Theory Under the Influence of External Conditions" (Benasque, Spain, 2011);
10 pages and 6 figure