No existence of the geometric potential for a Dirac fermion on a two-dimensional curved surface of revolution

For a free particle that moves non-relativistically on a curved surface, there are curvature-induced quantum potentials that significantly influence the surface quantum states. However, the experimental results in topological insulators, whether curved or not, indicate no evidence of such a potential for the relativistic particles constrained on the curved surface. Within the framework of Dirac quantization scheme, we demonstrate a general result that for a Dirac fermion on a two-dimensional curved surface of revolution, no curvature-induced quantum potential is permissible.     

Tunneling control of strongly correlated particles on a lattice: a photonic realization

We propose a photonic realization of tunneling control for two strongly correlated particles moving on a one-dimensional lattice, based on light transport in a square waveguide lattice with a periodically curved axis. We show the photonic analogue of dynamic localization of correlated particles and suggest the possibility to coherently suppress particle interaction.     

Development and application of a diffusion-inertia model for simulating gas-dispersed turbulent flows

The development and application of a diffusion-inertia model are shown for computing the propagation and deposition of aerosol particles in turbulent flows. Comparison with experimental and numerical results points to the fact that the developed model adequately describes all the typical peculiarities of the process of the sedimentation of aerosol particles in straight and curved pipes.     

On the surface analysis of small metal crystals

Small metal crystals as catalyst particles have often a surface which is composed not only of plane but also of curved faces. Using the example of the electron micrograph of a Pt particle an analysis is described which enables a determination of the orientation, the shape and the faces of a crystal. The analysis shows that the particle has a [320] orientation. The surface consists to ~ 37% of {111} faces, to ~ 28% of {100} faces and to ~ 35% of curved area. The curved region is mainly composed of {011}, {113}, {012} and {133} faces. The curved surface has the structure of a frozen state of thermal roughening. Such frozen structures have special adsorption sites in low concentration which in some cases may be important for the catalytic reaction.     

Pressure and Stress Tensor in a Yukawa Fluid

Systems of particles interacting through a screened Coulomb potential of the Debye–Yukawa form are considered. The pressure is obtained from the stress tensor of the field corresponding to the Yukawa interaction, by a suitable statistical average. This approach is especially appropriate for systems living in a curved space. In a curved space, a self contribution to the pressure appears, and it is essential to take it into account for retrieving a correct pressure when the Yukawa interaction tends to the Coulomb interaction.     

The renormalized stress-energy tensor and its associated operators for photons in curved four-dimensional space–time

We establish expressions for the renormalized stress-energy (or energy-momentum) tensor and its associated operators relative to photons as a Klein–Gordon field of non-zero rest-mass particles (with gravitational interaction) in curved four-dimensional space–time.     

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

We study self-assembly on a spherical surface of a model for a binary mixture of amphiphilic dimers in the presence of guest particles via Monte Carlo (MC) computer simulation. All particles had a hard core, but one monomer of the dimer also interacted with the guest particle by means of a short-range attractive potential. We observed the formation of aggregates of various shapes as a function of the composition of the mixture and of the size of guest particles. Our MC simulations are a further step towards a microscopic understanding of experiments on colloidal aggregation over curved surfaces, such as oil droplets.     

Squeezed Coherent State Representation of Scalar Field and Particle Production in the Early Universe

The quantum field theory of a scalar field in curved space-time is studied usingthe squeezed coherent state representation. In this representation the expectationvalues of the stress-energy tensor of the scalar field is calculated. The presentcalculation can account for the production of particles in the early universe.     

Geodesic deviation and particle creation in curved spacetimes

A quantum mechanical picture, relating accelerated geodesic deviation to creation of massive particles via quantum tunneling in curved background spacetimes, is presented. The effect is analogous to pair production by an electric field and leads naturally to production of massive particles in de Sitter and superluminal FRW spacetimes. The probability of particle production in de Sitter space per unit volume and time is computed in a leading semiclassical approximation and shown to coincide with the previously obtained expression.     

Structural transformation of graphite by arc-discharge

The formation of novel structures by the passage of an electric current through graphite is described. These structures apparently consist of hollow three-dimensional graphitic shells bounded by curved and faceted planes, typically made up of two graphene layers. The curved structures were frequently decorated with nano-scale carbon particles, or short nanotubes. In some cases, nanotubes were found to be seamlessly connected to the thin shells, indicating that the formation of the shells and the nanotubes is intimately connected. Small nanotubes or nanoparticles were also sometimes found encapsulated inside the hollow structures, while fullerene-like particles were often seen attached to the outside surfaces. With their high surface areas and structural perfection, the new carbon structures may have applications as anodes of lithium ion batteries or as components of composite materials.     

Symmetries and Motions in NUT-Taub Spinning Space

We review the geodesic motion of pseudo-classical spinning particles in curved space. We describe the generalized Killing equations for spinning spaces and express the constants of motion. We apply the formalism to solve for the motion of a pseudo-classical Dirac fermion in NUT-Taub spinning space and analyze the motion on a cone and on a plane.     

Spinning Particles in Curved Spacetime

We briefly discuss the relevant equations for the motion of spinning particles in curved spacetime. We describe the generalized Killing equations for spinning spaces and derive the constants of motion. We apply the formalism to solve for the motion of a pseudoclassical spinning particle in Schwarzschild–de Sitter spacetime.     

非对称弯曲微流道中粒子惯性聚焦动态过程及流速调控机理研究

设计制作了一种具有非对称弯曲微流道结构的微流控芯片, 搭建实验平台定量表征聚苯乙烯粒子和血细胞沿流道的动态惯性聚焦过程, 并系统研究了流体流速和粒子尺寸对粒子聚焦特性的调控机理. 通过分析粒子荧光图谱和对应量化强度曲线, 将粒子沿流道长度的横向迁移过程分为形成聚焦和平衡位置调整两个阶段, 指出在整个聚焦过程中具有小曲率半径的流道结构起主导作用. 根据全流速段内粒子聚焦特性的演变, 重点分析潜在惯性升力和Dean 曳力的竞争机制, 提出了阐述粒子聚焦流速调控过程的三阶段模型. 进一步比较两种尺寸粒子聚焦位置和聚焦率随流速与流道长度的变化规律, 发现大粒子具有更好的聚焦效果和稳定性, 且两种粒子的相对位置可通过流速进行调整. 最后, 通过分析血细胞在非对称弯流道中的横向迁移特性, 验证了粒子惯性聚焦机理在复杂生物粒子操控方面的适用性. 上述结论为深入研究微流体环境下粒子的运动特性以及开发微流式细胞术等临床即时诊断器件提供了重要参考.     

Incoherent radiation of fast electrons in a crystalline undulator

Incoherent radiation of high-energy particles in a crystal is caused by the thermal scattering of atoms relative to their equilibrium lattice positions. An earlier developed procedure for incoherent radiation simulation is applied to the case of electron motion in a sinusoidally curved crystal. The simulation results agree with the data of recent experiments at the Mainz Microtron (MAMI).     

Gravitational Spin Entropy Production

Spin entropy production for particles with arbitrary spin moving in a curved spacetime is discussed. There is a Wigner rotation due to both the acceleration an the curvature, which causes an initial pure state to transform into a final mixed state. Depending on the spacetime characteristics, one may find paths on which there is no Wigner rotation and the state remains pure.     

Supersymmetries and Constants of Motion in Taub-NUT Spinning Space

We review the geodesic motion of pseudo-classical spinning particles in curved spaces. Investigating the generalized Killing equations for spinning spaces, we express the constants of motion in terms of Killing-Yano tensors. The general results are applied to the case of the four-dimensional Euclidean Taub-NUT spinning space. A simple exact solution, corresponding to trajectories lying on a cone, is given.     

Entangled quantum fields near the event horizon and entropy

By fully exploiting the existence of the unitarily inequivalent representations of quantum fields, we exhibit the entanglement between inner and outer particles, with respect to the event horizon of a black hole. We compute the entanglement entropy and we find that the non-unitarity of the mapping, between the vacua in the flat and the curved frames, makes the entanglement very robust.     

Some Far-Field Scattering Characteristics of Radially Inhomogeneous Particles

The finely stratified sphere model was used to calculate scattered electromagnetic fields from radially inhomogeneous spherical particles illuminated by electromagnetic plane waves. The calculation results show that radial gradients of the real part of the refractive indices change the ray paths into curved lines inside large spherical particles, resulting in fluctuations of rainbow positions for droplets during heat transfer processes. The light intensity in the forward scattering region is found to be useful to infer information about the profile of the imaginary part of the refractive index.     

Quantum corrections to the spacetime metric from geometric phase space quantization

We consider the possibility that the physical spacetime of a quantum particle may be regarded as a four-dimensional hypersurface locally embedded in eightdimensional phase space. We show that, as a consequence, accelerated particles are seen to live in a curved spacetime, and, in the particular case of uniform acceleration, we are led to a generalization of the Rindler metric which implies, for a uniformly accelerated particle, a discrete energy spectrum.