Effect of the size of macroparticles on their electrostatic interaction in a plasma

The electrostatic interaction of two spherical macroparticles in a plasma has been considered. Primary attention has been focused on investigating the electrostatic interaction at short distances where polarization effects of the surface charge of finite-size macroparticles begin to play a dominant role. The first part of this study is devoted to the interaction of a point charge with a charged conducting sphere in an equilibrium plasma. It has been shown that the presence of a plasma in the system leads to a decrease in the potential barrier when two like-charged macroparticles approach each other and that this decrease proves to be the most significant in the case where the macroparticle radius is comparable to the Debye screening length. The second part of this study is concerned with the interaction of two conducting spheres in the bispherical system of the coordinates under the assumption that the charges of the conducting spheres are constant and under the assumption that the surface potentials of the spheres are constant. The latter case is closer to the physics of electrostatic interaction of two macroparticles in a plasma medium where the electrostatic potential of their surface is determined by the floating potential of the plasma. It has been demonstrated that the interaction potentials in these two cases are substantially different from each other and that, at constant macroparticle charges, the energy of the electrostatic field is an interaction potential, but, in the case of macroparticles with constant surface potentials, which are independent of the interparticle distance, the energy of the electrostatic field is not an interaction potential. In the latter case, account must be taken of the work done by external sources on the macroparticle potentials to maintain them constant. The form of the interaction potential has been established in this case from the analysis of the interaction force in terms of the Maxwell tension tensor. In the third part of this study, the interaction of two macroparticles has been considered in the spherical system of coordinates and analytical expressions for the interaction potentials have been derived for both the case of constant macroparticle charges and the case of constant surface potentials of the macroparticles.     

两个双能级原子与双模腔场的拉曼相互作用

研究了两个双能级原子与双模辐射腔场的拉曼相互作用，计算了两个原子与腔场具有相同耦合常数但同时考虑原子间偶极一偶极相互作用情形下的辐射谱．讨论了双模腔场处于不同数态时辐射谱的新特点．     

有倾斜透镜存在时两个刃型位错的相互作用

对存在倾斜透镜时两个刃型位错的相互作用进行了研究.研究表明, 两个离轴刃型位错在一定条件下由于相互作用会消失, 并有一个或两个非正则光涡旋产生, 一个共轴刃型位错和一个离轴刃型位错相互作用时产生一个非正则光涡旋. 当初始场中两个刃型位错相互垂直或者平行时, 出射场中会有一个或者两个刃型位错出现. 改变透镜的倾斜因子不影响出射场中位相奇点的类型和数量, 但位相奇点的横向位置与倾斜因子有线性关系. 两个刃型位错相互作用产生的光涡旋对的三维轨迹是非线性的, 但光涡旋对的中心沿直线传输. 关键词： 位相奇点 刃型位错 非正则光涡旋 倾斜透镜     

Interaction of two macroparticles in a nonequilibrium plasma

The interaction of two macroparticles in a nonequilibrium plasma at elevated pressures has been investigated. An asymptotic theory of screening, which leads to a two-exponential dependence of the macroparticle potential on distance with different screening constants, is used to determine the electrostatic energy of the system of charges associated with the two macroparticles. The dependence of the electrostatic energy on interparticle distance has been found to have a minimum, as in an equilibrium plasma. The interaction force between the macroparticles has been determined; it turned out to be asymmetric—for different charges, the forces acting on the first and second macroparticles are not equal. This is the result of an asymmetric charge separation near macroparticles with differing charges and indicates that the interaction force in a nonequilibrium plasma is nonpotential. The forces are equal for identical macroparticles or in an equilibrium plasma and the potential energy of the interaction between the macroparticles has been determined for these cases. Attraction between likely charged particles with different (in magnitude) charges has been found to be possible when they come very close together. Relations to determine the modified coupling parameter for an interaction potential that consists of two exponential terms with different screening constants have been derived.     

Optical properties of a system of two coupled vertical microcavities

The interaction of two localized optical states in a structure consisting of a system of two coupled vertical microcavities is studied. It is shown that the interaction of two localized optical modes in coupled microcavities cause the modes to split. The optical properties of a system of coupled microcavities and the dispersion relations for the characteristic optical modes of the system are analyzed. Zh. Tekh. Fiz. 68, 94–97 (May 1998)     

Nonlinear Wave in a Disc-Shaped Bose-Einstein Condensate

We discuss the possible nonlinear waves of atomic matter wave in a Bose-Einstein condensate. One and two of two-dimensional （2D） dark solitons in the Bose-Einstein condensed system are investigated. A rich dynamics is studied for the interactions between two solitons. The interaction profiles of two solitons are greatly different if the angle between them are different. If the angle is small enough, the maximum amplitude during the interaction between two solitons is even less than that of a single soliton. However, if the angle is large enough, the maximum amplitude of two solitons can gradually attend to the sum of two soliton amplitudes.     

Modelling the interaction in a benzene dimer

The interaction between aromatic rings is a fundamental problem in material science and biochemistry. These interactions are generally found to stabilise protein molecules and the double helical structure of DNA, and they also play an important role in the recognition processes in biological and non-biological systems. However, the complexity and variety in the structures and components of aromatic compounds are major obstacles to investigating their interactions. In this study, the simplest case of aromatic interactions, which is the interaction between two benzene rings, is modelled using a continuous approximation. Assuming a constant atomic surface density and modelling the structure of a benzene molecule as a combination of two rings, namely an inner carbon ring and an outer hydrogen ring, the van der Waals interaction between any two benzene rings can be obtained as the sum of four interactions. The major result obtained here is an analytical expression for the potential energy which can then be used to predict equilibrium configurations for two interacting benzene molecules. Moreover, we find that at sufficiently large distances between the two benzene molecules, the orientational angle φ at which the interaction energy is a minimum can be approximated by the arctan of the ratio of two separation distances in two mutually perpendicular directions.     

Quantum fields and poisson processes II: Interaction of boson-boson and boson-fermion fields with a cut-off

Quantum field evolutions are written as expectation values with respect to Poisson processes in two simple models: interaction of two boson fields (with conservation of the number of particles in one field) and interaction of a boson with a fermion field. The introduction of a cut-off ensures that the expectation values are well-defined.     

Experimental investigation of the three-dimensional interaction of a strong shock with a spherical density inhomogeneity

Laser-driven experiments are described which probe the interaction of a very strong shock with a spherical density inhomogeneity. The interaction is viewed from two orthogonal directions enabling visualization of both the initial distortion of the sphere into a double vortex ring structure as well as the onset of an azimuthal instability that ultimately results in the three-dimensional breakup of the ring. The experimental results are compared with 3D numerical simulations and are shown to be in remarkable agreement with the incompressible theory of Widnall et al. [J. Fluid Mech. 66, 35 (1974)].     

Coulomb interactions in a computer simulation of a system periodic in two directions

The integral representation of the gamma function and the Poisson summation formula are used to calculate the interaction energy of charged particles in a 3-dimensional system periodic in two directions. A parallelogram shape simulation box is considered. Calculations are carried out for interactions described by any inverse power, and analytical continuation of the energy function leads to the final expression for the Coulomb interaction energy. Summation over the simulation box replica along one or the other side of the box base is replaced by summation in reciprocal space. Therefore there are two equivalent formulas for the potential energy that offer the possibility of avoiding slowly convergent series. The energy expressions are identical to those obtained from the Lekner method. The special case is considered where the functions defining the energy are infinite, i.e. when two charges lie on a line parallel to the simulation box side that was chosen to convert real space summation into reciprocal space.     

Evolution of initial distributions with one and two centers in a two-dimensional model of the reaction-diffusion type with a nonlocal interaction of finite radius

Solutions of a generalized Fisher–Kolmogorov–Petrovskii–Piskunov equation for a nonlocal interaction of finite radius have been constructed for initial conditions with one and two localization centers by using numerical methods. The dynamics depends on the choice of the equation parameters and initial conditions. The processes of formation and interaction of the rings expanding from each of the two localization centers and the formation of dissipative structures are considered.     

The Casimir interaction of a massive vector field between concentric spherical bodies

The Casimir interaction energy due to the vacuum fluctuations of a massive vector field between two perfectly conducting concentric spherical bodies is computed. The TE contribution to the Casimir interaction energy is a direct generalization of the massless case but the TM contribution is much more complicated. Each TM mode is a linear combination of a transverse mode which is the generalization of a TM mode in the massless case and a longitudinal mode that does not appear in the massless case. In contrast to the case of two parallel perfectly conducting plates, there are no TM discrete modes that vanish identically in the perfectly conducting spherical bodies. Numerical simulations show that the Casimir interaction force between the two bodies is always attractive.     

Splitting dynamics of a two-species Bose-Einstein condensate in two translating traps

We extend our previous work of splitting a single-species Bose-Einstein condensate in two translating traps to a two-species condensate. Different from the single species case where interaction is considered as a damping mechanism to the motion of the condensate, we find that, in the two species case, the damping effect is much less obvious and the splitting dynamics exhibit different behaviors. The distribution of each component are not damped towards 50:50 for large interaction strength in the two wells. Our conclusions are supported by investigating the dependence of the splitting on both the translation speed and the interspecies scattering length.     

Correlated motion of a pair of electrons in a random alloy

A theory of dynamical electron-electron correlation in a random A_xB_1?x alloy is developed as an extension to the Kanamori model: two electrons in a narrow band, interacting via randomly varying contact pair interaction are considered. The exact theory, including exact moments and localization theorems, is derived. A coherent potential approximation in the space of two-particle states, describing the effect of the pair interaction quite exactly, is then developed. The case with randomness in the pair interaction only is discussed in detail. Results of numerical analysis for a simple model based on the scaling-factor approximation are given to illustrate the essential features of the CPA solution.     

Density of states for a disordered system of interacting dipoles

The density of states for a system of interacting Ising dipoles in the presence of diagonal disorder is obtained by computer simulation. Two models are considered, one with the true dipole-dipole interaction and another in which the angular dependence of the interaction is not included. Results for different values of the disorder energy are obtained for the two models, fitting quite well to previous analytical calculations.     

Influence of six-quark bags on the NN interaction in a resonating group scattering calculation

The influence of six-quark bags on the nucleon-nucleon (NN) interaction is studied in a dynamical calculation of the NN scattering process. The NN interaction is described by the exchange of gluons and pions between quarks and a phenomenological σ-meson exchange between nucleons. The quark wave functions are harmonic oscillators and the relative wave function between the two nucleons is determined by the resonating group method. At short distances the NN system is allowed to fuse to a six-quark bag where all six quarks are in a ground state or where two quarks are in excited Op states. The sizes of these six-quark bags are dynamical parameters in the resonating group calculation allowing for spatial polarisation effects during the interaction. The S-wave NN scattering data can be reproduced by adjusting the σ-coupling strength. The main result is that the six-quark bags with an increased radius have a large influence on the NN scattering process.     

Quantum search via superconducting quantum interference devices in a cavity

We propose a scheme for implementing the Grover search algorithm with two superconducting quantum interference devices (SQUIDs) in a cavity. Our scheme only requires single resonant interaction of the SQUID-cavity system and the required interaction time is very short. The simplicity of the process and the reduction of the interaction time are important for restraining decoherence.     

Josephson junction of two-species Bose-Einstein condensates in a high-finesse optical cavity

The mean-field dynamics of undistinguishable two-species Bose Josephson junction coupled to a single mode high-finesse optical cavity is investigated.From the Hamiltonian,the phase portrait and the stationary points are given.It is shown that the role of the interspecies interaction equals the intraspecies interaction under suitable conditions.As the interspecies interaction increases,the trapped atoms will start tunneling between the two wells unnaturally for some special cases.     

Elastic interaction of two atoms adsorbed on a solid surface

The long-range interaction of two adsorbed atoms mediated by the elastic distortion of the substrate is calculated classically for an elastically isotropic substrate. For identical atoms, the interaction is repulsive; for different atoms, it can be repulsive or attractive. It varies as ρ^?3 with the distance ρ between the two adsorbed atoms. This is the same spatial dependence as for the dipole - dipole interaction between two adsorbed atoms. For two xenon atoms adsorbed on gold, the elastic interaction is somewhat smaller than the dipole-dipole interaction. The interaction energy is inversely proportional to the shear modulus of the substrate, so that it may become quite large near a distortive phase transition.     

The energy levels of a two-electron two-dimensional parabolic quantum dot

This paper studies the two-electron total energy and the energy of the electron--electron interaction by using a variational method of Pekar type on the condition of electric--LO-phonon strong coupling in a parabolic quantum dot. It considers the following three cases: 1) two electrons are in the ground state; 2) one electron is in the ground state, the other is in the first-excited state; 3) two electrons are in the first-excited state. The relations of the two-electron total energy and the energy of the electron--electron interaction on the Coulomb binding parameter, the electron-LO-phonon coupling constant and the confinement length of the quantum dot are derived in the three cases.