1,721,022 research outputs found
Casimir and Casimir-Polder interactions for magneto-dielectric materials: Surface scattering expansion
Full text linkInternational audienceWe develop a general multiple scattering expansion (MSE) for computing Casimir forces between magneto-dielectric bodies and Casimir-Polder forces between polarizable particles and magneto-dielectric bodies. The approach is based on fluctuating electric and magnetic surface currents and charges. The surface integral equations for these surface fields can be formulated in terms of surface scattering operators (SSO). We show that there exists an entire family of such operators. One particular member of this family is only weakly divergent and allows for a MSE that appears to be convergent for general magneto-dielectric bodies. We proof a number of properties of this operator, and demonstrate explicitly convergence for sufficiently low and high frequencies, and for perfect conductors. General expressions are derived for the Casimir interaction between macroscopic bodies and for the Casimir-Polder interaction between particles and macroscopic bodies in terms of the SSO, both at zero and finite temperatures. An advantage of our approach above previous scattering methods is that it does not require the knowledge of the scattering amplitude (T-operator) of the bodies. A number of simple examples are provided to demonstrate the use of the method. Some applications of our approach have appeared previously [T. Emig, G. Bimonte, Phys. Rev. Lett. 130, 200401 (2023)]. Here we provide additional technical aspects and details of our approach
Temperature distribution and heat radiation of patterned surfaces at short wavelengths
Full text linkWe analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape
Something Can Come of Nothing: Surface Approaches to Quantum Fluctuations and the Casimir Force
Full text linkThe Casimir force provides a striking example of the effects of quantum
fluctuations in a mesoscopic system. Because it arises from the objects'
electromagnetic response, the necessary calculations in quantum field theory
are most naturally expressed in terms of electromagnetic scattering from each
object. In this review we illustrate a variety of such techniques, with a focus
on those that can be expressed in terms of surface effects, including both
idealized boundary conditions and their physical realization in terms of
material properties.Comment: 29 pages, 2 figures; invited contribution to Annual Reviews in
Nuclear and Particle Science; v2: minor editing of version for publicatio
Multiple scattering expansion for dielectric media: Casimir effect
Full text linkRecent measurements of Casimir forces have provided evidence of an intricate
modification of quantum fluctuations of the electromagnetic field in complex
geometries. Here we introduce a multiple scattering description for Casimir
interactions between bodies of arbitrary shape and material composition,
admitting an expansion as a sequence of inter- and intra-body wave scatterings.
Interactions in complex geometries can be computed within the current
experimental resolution from typically a few wave scatterings, notably without
any a priori knowledge of the scattering amplitudes of the bodies. Some first
applications demonstrate the power of the approach.Comment: 6 pages, 4 figure
Casimir-Polder force between anisotropic nanoparticles and gently curved surfaces
Full text linkThe Casimir-Polder interaction between an anisotropic particle and a surface is orientation dependent.
We study novel orientational effects that arise due to curvature of the surface for distances much
smaller than the radii of curvature by employing a derivative expansion. For nanoparticles we derive a
general short distance expansion of the interaction potential in terms of their dipolar polarizabilities.
Explicit results are presented for nano-spheroids made of SiO2 and gold, both at zero and at finite
temperatures. The preferred orientation of the particle is strongly dependent on curvature, temperature, as
well as material properties
Scattering theory approach to electrodynamic Casimir forces
No full textWe give a comprehensive presentation of methods for calculating the Casimir force to arbitrary accuracy, for any number of objects, arbitrary shapes, susceptibility functions, and separations. The technique is applicable to objects immersed in media other than vacuum, nonzero temperatures, and spatial arrangements in which one object is enclosed in another. Our method combines each object’s classical electromagnetic scattering amplitude with universal translation matrices, which convert between the bases used to calculate scattering for each object, but are otherwise independent of the details of the individual objects. The method is illustrated by rederiving the Lifshitz formula for infinite half-spaces, by demonstrating the Casimir-Polder to van der Waals crossover, and by computing the Casimir interaction energy of two infinite, parallel, perfect metal cylinders either inside or outside one another. Furthermore, it is used to obtain new results, namely, the Casimir energies of a sphere or a cylinder opposite a plate, all with finite permittivity and permeability, to leading order at large separation
Electromagnetic Casimir energy of a disk opposite a plane
Full text linkBuilding on work by J. Meixner [Z. Naturforschung 3a, 506 (1948)], we show how to compute the exact scattering amplitude (or T-matrix) for electromagnetic scattering from a perfectly conducting disk. This calculation is a rare example of a nondiagonal T-matrix that can nonetheless be obtained in a semianalytic form. We then use this result to compute the electromagnetic Casimir interaction energy for a disk opposite a plane, for arbitrary orientation angle of the disk, for separations greater than the disk radius. We find that the proximity force approximation (PFA) significantly overestimates the Casimir energy, in the case of both the ordinary PFA, which applies when the disk is parallel to the plane, and the “edge PFA”, which applies when the disk is perpendicular to the plane
Many-body heat radiation and heat transfer in the presence of a nonabsorbing background medium
Full text linkHeat radiation and near-field radiative heat transfer can be strongly manipulated by adjusting geometrical shapes, optical properties, or the relative positions of the objects involved. Typically, these objects are considered as embedded in vacuum. By applying the methods of fluctuational electrodynamics, we derive general closed-form expressions for heat radiation and heat transfer in a system of N arbitrary objects embedded in a passive nonabsorbing background medium. Taking into account the principle of reciprocity, we explicitly prove the symmetry and positivity of transfer in any such system. Regarding applications, we find that the heat radiation of a sphere as well as the heat transfer between two parallel plates is strongly enhanced by the presence of a background medium. Regarding near- and far-field transfer through a gas like air, we show that a microscopic model (based on gas particles) and a macroscopic model (using a dielectric contrast) yield identical results. We also compare the radiative transfer through a medium like air and the energy transfer found from kinetic gas theory
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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