We measure the Casimir force between a gold sphere and a silicon plate with nanoscale, rectangular corrugations with a depth comparable to the separation between the surfaces. In the proximity force approximation (PFA), both the top and bottom surfaces of the corrugations contribute to the force, leading to a distance dependence that is distinct from a flat surface. The measured Casimir force is found to deviate from the PFA by up to 10%, in good agreement with calculations based on scattering theory that includes both geometry effects and the optical properties of the material.
We compute the radiative heat transfer between nanostructured gold plates in the framework of the scattering theory. We predict an enhancement of the heat transfer as we increase the depth of the corrugations while keeping the distance of closest approach fixed. We interpret this effect in terms of the evolution of plasmonic and guided modes as a function of the grating's geometry.
We present a theoretical study of radiative heat transfer between dielectric nanogratings in the scattering approach. As a comparison with these exact results, we also evaluate the domain of validity of Derjaguin's proximity approximation (PA). We consider a system of two corrugated silica plates with various grating geometries, separation distances, and lateral displacement of the plates with respect to one another. Numerical computations show that while the PA is a good approximation for aligned gratings, it cannot be used when the gratings are laterally displaced. We illustrate this by a thermal modulator device for nanosystems based on such a displacement.
We present detailed calculations for the Casimir force between a plane and a nanostructured surface at finite temperature in the framework of the scattering theory. We then study numerically the effect of finite temperature as a function of the grating parameters and the separation distance. We also infer nontrivial geometrical effects on the Casimir interaction via a comparison with the proximity force approximation. Finally, we compare our calculations with data from experiments performed with nanostructured surfaces.
Quantitative finance has had a long tradition of a bottom-up approach to complex systems inference via multi-agent systems (MAS). These statistical tools are based on modelling agents trading via a centralised order book, in order to emulate complex and diverse market phenomena. These past financial models have all relied on so-called zero-intelligence agents, so that the crucial issues of agent information and learning, central to price formation and hence to all market activity, could not be properly assessed. In order to address this, we designed a next-generation MAS stock market simulator, in which each agent learns to trade autonomously via reinforcement learning. We
We study the lateral dependence of the Casimir energy for different corrugated gratings of arbitrary periodic profile. To this end we model the profiles as stacks of horizontal rectangular slices following the profiles' shape and evaluate numerically the Casimir energy between them for different relative lateral displacements of the two corrugated plates. We compare our results with predictions obtained within the proximity force approximation (PFA). At comparable separation of the corrugated plates and geometric parameters, we find a strong dependence of the Casimir energy on the shape of the corrugation profiles.
We compute the radiative heat transfer between nanostructured gold plates in the framework of the scattering theory. We predict an enhancement of the heat transfer as we increase the depth of the corrugations while keeping the distance of closest approach fixed. We interpret this effect in terms of the evolution of plasmonic and guided modes as a function of the grating's geometry. PACS numbers: 64.70.Nd, 44.40.+a, 44.05.+e The far-field radiative heat transfer between good conductive metals is very low at room temperature, since they are very good reflectors at the infrared frequencies of blackbody radiation. The radiative heat transfer is enhanced in the near field, due to the contribution of evanescent surface modes [1][2][3]. Polar materials like SiO 2 or SiC are in addition favored by the contribution of surface phonon polaritons whose resonance frequencies lie in the infrared [4]. There is an analogous effect for metals arising from the surface plasmons resonances but those lie in the ultraviolet and do not contribute significantly to the heat transfer [5].It has been shown recently that the radiative heat transfer can be controlled by nanostructuring the interfaces periodically. When the period d is much smaller than the wavelength λ and the separation distance L, the system can be treated using an effective refractive index for the equivalent homogeneous medium. It has been shown that the induced anisotropy introduces additional modes [6] and also allows modulating the flux [7]. For periods on the order of the wavelength, a full solution of Maxwell equations is needed. The heat transfer between two periodic slabs has been studied within a two dimensional approximation and for p-polarization using a finite difference time domain (FDTD) technique [8]. A flux enhancement attributed to the excitation of the structure's modes was found. While FDTD allows modeling complex shapes easily, dealing with bulk 3D media and accounting for polarization effects has not been achieved so far.In this letter, we compute the radiative heat transfer between 1D gold lamellar gratings in the framework of the scattering theory. We do include all propagation directions (the so-called conical diffraction) and all polarization states, which is of critical importance in order to deal quantitatively with cross-polarization effects [9]. The scattering theory is the most successful technique for treating the Casimir effect between bodies at thermodynamic equilibrium [10,11]. The method determines the electromagnetic field in the space between the two bodies in interaction in order to compute the Maxwell stress tensor in terms of the reflection amplitudes on the two bodies. When the two bodies are not at the same temperature, there is a net flux of energy transferred from the warm body to the cold one. Recently, this heat transfer problem between two bodies kept at different temperatures has also been formulated in terms of the scattering properties of the bodies [12][13][14][15].In the following, we use the scattering amplitudes wh...
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