Drag force of moving quark in STU background

In this paper we consider a quark moving in D=5, supergravity thermal plasma. By using the three charges non-extremal black hole solution (STU solution) we calculate the drag force on the quark and the diffusion constant from the AdS/CFT correspondence.     

On asymptotics of the solution of the moving oscillator problem

Asymptotic behavior of the solution of the moving oscillator problem is examined for large and small values of the spring stiffness for the general case of non-zero beam initial conditions. In the limiting case of infinite spring stiffness, it is shown that the moving oscillator problem for a simply supported beam is not equivalent, in a strict sense, to the moving mass problem. The two problems are shown to be equivalent in terms of the beam displacements but are not equivalent in terms of stresses (the higher order derivatives of the two solutions differ). In the general case, the force acting on the beam from the oscillator is shown to contain a high-frequency component , which does not vanish and can even grow when the spring coefficient tends to infinity. The magnitude of this force and its dependence on the oscillator parameters can be estimated by considering the asymptotics of the solution for the initial stage of the oscillator motion. It is shown that, for the case of a simply supported beam, the magnitude of the high-frequency force depends linearly on the oscillator eigenfrequency and velocity. The deficiency of the moving mass model is principally that it fails to predict stresses in the supporting structure. For small values of the spring stiffness, the moving oscillator problem is shown to be equivalent to the moving force problem. The discussion is amply illustrated by results of numerical experiments.     

Electrodynamics of moving media and the force on a current loop

The development of the Chu formulation of the electrodynamics of moving media is reviewed. The force on a current loop and/or magnetic dipole is developed for three different models and all three are shown to be identical, as already shown in previous publications. The electromagnetic momentum associated with the three different models is derived and the equality of the force expressions is confirmed on the basis of the momentum conservation theorem of electrodynamics. The paper is based on a lecture delivered at Technion at the occasion of Professor Franz Ollendorff's 80th birthday.     

Derivation of the transverse force on a moving vortex in a superfluid

We describe an exact derivation of the total nondissipative transverse force acting on a quantized vortex moving in a uniform background. The derivation is valid for neutral boson or fermion superfluids, provided the order parameter is a complex scalar quantity. The force is determined by the one-particle density matrix far away from the vortex core, and is found to be the Magnus force proportional to the superfluid density.     

Non-stationary response of a beam to a moving random force

The non-stationary random vibration of a beam is investigated. The beam is subjected to a random force with constant mean value which is moving with constant speed along the beam. The statistical characteristics of the first and second order for the deflection and bending moment of the beam are computed by using the correlation method. The numerical results of the coefficient of variation of the deflection at beam span mid-point are given for five basic types of convariances of the force (white noise, constant, exponential cosine, exponential, and cosine wave). The effect of the speed of the movement of the force along the beam as well as the effect of the beam damping is investigated in detail. It is concluded that the resulting beam vibration turns out to be a non-stationary process even though the motion considered is that of a stationary random force.     

双色激光场对运动原子的辐射压力

本文研究了双色行波场对运动原子的辐射压力，通过数值计算，分别得到了在不同光强，不同频率，不同传播方向条件下，原子在双色场中的受激跃迁速率和辐射压力随速度变化的关系。结果表明：双色场对原子的辐射压力和行波场及驻波场相比，有着许多不同特点，这些特点可以在激光冷却中性原子，原子速度选择，原子动量扩散的研究中加以利用。     

Deforming and moving a vortex by the tip of a magnetic force microscope

Recent experiments [O.M. Auslaender et al., Nat. Phys. 5 (2009) 35] use a magnetic force microscope not only to image but also to move and deform an individual vortex line in a bulk YBCO type-II superconductor. The theory of this experiment is presented accounting for pinning and curving of the vortex and for the full three-dimensional anisotropy of pinning and of vortex line tension in this material.     

Dynamic stability of thermoelastic coupling moving plate subjected to follower force

The dynamic characteristics and stability of the moving thermoelastic coupling rectangular plate subjected to uniformly distributed tangential follower force are investigated. Based on the heat conduction equation containing the thermoelastic coupling term and the thin plate theory, the thermoelastic coupling differential equation of motion of the rectangular plate under the action of uniformly distributed tangential follower force is established. Dimensionless complex frequencies of the moving thermoelastic coupling rectangular plate with four edges simply supported, two opposite edges simply supported and other two edges clamped are calculated by the differential quadrature method. The effects of the dimensionless thermoelastic coupling factor and dimensionless moving speed on the stability and critical load of the moving plate are analyzed. The results show that the divergence loads of the first order mode increase with the increase of the dimensionless thermoelastic coupling factor, and decrease with increasing the dimensionless moving speed.     

Drag force on a moving heavy quark with deformed string configuration

To study drag force on a moving heavy quark through a plasma, we use a deformed AdS space-time, in which deformation parameter c describes non-conformality in AdS/QCD. In this case, the quark is mapped to a probe string in the AdS space. Considering the probable contribution of the deformation parameter in the probe string, we apply a general form of c-dependent string ansatz in the drag force computation. Then, we find the acceptable value of this parameter as it satisfies QCD calculations. Using this result, we also discuss the diffusion constant which is in agreement with the phenomenological result for the non-relativistic limit. Also, we show that while in absence of a deformation parameter, the probe string is a strictly increasing function of radial coordinate, the c-dependent probe string has a maximum value versus z.     

用惯性力分析二体问题

利用惯性力分析二体问题.     

A diffusion problem in a region with a moving boundary

We consider the first linear diffusion problem in a semiinfinite region with a boundary moving in accordance with a quadratic law. For the case of uniformly decelerating motion of the boundary, the solution of the problem is obtained by the Green's function, method under the most general boundary conditions; the solution of the problem for the case of uniformly accelerated motion of the boundary is obtained by an operator method.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 102–110, December, 1970.     

Casimir friction force and energy dissipation for moving harmonic oscillators. II

This paper is a second in a series devoted to the study of a two-oscillator system in linear relative motion (the first one published as a letter in [J.S. H?ye, I. Brevik, Europhys. Lett. 91, 60003 (2010)]). The main idea behind considering this kind of system is to use it as a simple model for Casimir friction. In the present paper we extend our previous theory so as to obtain the change in the oscillator energy to second order in the perturbation, even though we employ first order perturbation theory only. The results agree with, and confirm, our earlier results obtained via different routes. The friction force is finite at finite temperatures, whereas in the case of two oscillators moving with constant relative velocity the force becomes zero at zero temperature, due to slowly varying coupling.     

Three-body scattering at positive energies: Solving the problem of moving logarithmic singularities

For three-body scattering at positive total energies, integral equations are obtained whose kernels have no logarithmic singularities on the contour of integration. The corresponding singularities that are present in original integral equations can be circumvented by shifting a part of the contour of integration from the real axis to the complex plane. This is done only for a special auxiliary solution appearing to be an analytic function in this region. The physical amplitude proper is found as one of the solutions to the resulting set of equations. In contrast to conventional techniques, an additional analysis is therefore not required here, so that numerical solutions can be obtained within standard computational schemes.     

力梯度辛方法在圆型限制性三体问题中的应用

旋转坐标系下的圆型限制性三体问 题因含非惯性系所附加的影响部分使得动能不是动量的严格二次型, 可能导致力梯度辛积分算法的应用遇到困难. 从Lie算子运算出发, 严格论证了力梯度算子在这种情形下的物理意义 仍然像质心惯性坐标系下的圆型限制性三体问题那样是引力的梯度, 而不是引力与非惯性力所得合力的梯度, 表明了力梯度辛方法适合求解旋转坐标系下的圆型限制性三体问题. 通过应用四阶力梯度辛方法、最优化四阶力梯度辛方法和Forest-Ruth 辛方法分别求解该问题, 进行了数值对比研究, 结果显示最优化型力梯度算法能够取得最好精度. 还应用最优化型算法计算两邻近轨道的Lyapunov指数和快速Lyapunov指标, 确保高精度辛方法能够贯穿于这些混沌指标计算的全过程, 以便准确刻画此系统的动力学定性性质. 关键词： 辛积分器 圆型限制性三体问题 混沌 Lyapunov指数