The Physical Tourist Physics in Glasgow: A Heritage Tour

I trace the history of the physical and applied sciences, and particularly physics, in Glasgow. Among the notable individuals I discuss are Joseph Black (1728–1799), James Watt (1736–1819), William John Macquorn Rankine (1820–1872), William Thomson, Lord Kelvin (1824–1907), John Kerr (1824–1907), Frederick Soddy (1877–1956), John Logie Baird (1888–1946), and Ian Donald (1910–1987), as well as physics-related businesses.The locations, centering on the city center and University of Glasgow, include sites both recognizable today and transformed from past usage, as well as museums and archives related to the history and interpretation of physics.     

激光惯性约束聚变中光学汤姆逊散射研究进展

当前,激光惯性约束聚变在越来越接近点火的极端能量密度条件下,实验与模拟的偏离逐渐增大,一个关键原因是缺乏对黑腔等离子体状态及其影响黑腔能量学和内爆对称性的细致研究和判断。光学汤姆逊散射主动式、诊断精确、参数完备的优点,使之成为激光惯性约束聚变黑腔等离子体状态参数精密诊断的标准方法。中国面向激光惯性约束聚变研究的光学汤姆逊散射实验技术的发展与神光系列激光装置的建设和在其上开展的物理实验紧密相关。近年来,四倍频汤姆逊散射实验技术在神光III原型和100 kJ激光装置上相继建立,部分实验结果不仅加深了对激光惯性约束聚变靶物理的认识,还反映了实验条件对汤姆逊散射诊断的影响,促进了实验技术的精密化发展。在未来,还需要进一步发展多支路汤姆逊散射、五倍频汤姆逊散射和超热相干汤姆逊散射等新技术,面向点火黑腔条件,大幅提升激光等离子体状态参数的诊断精度,开展新物理机制的探索和研究,在激光惯性约束聚变和其他高能量密度物理科学领域发挥更重要的作用。     

The Observer in the Quantum Experiment

A goal of most interpretations of quantum mechanics is to avoid the apparent intrusion of the observer into the measurement process. Such intrusion is usually seen to arise because observation somehow selects a single actuality from among the many possibilities represented by the wavefunction. The issue is typically treated in terms of the mathematical formulation of the quantum theory. We attempt to address a different manifestation of the quantum measurement problem in a theory-neutral manner. With a version of the two-slit experiment, we demonstrate that an enigma arises directly from the results of experiments. Assuming that no observable physical phenomena exist beyond those predicted by the theory, we argue that no interpretation of the quantum theory can avoid a measurement problem involving the observer.     

Correspondence between Electrostatics and Contact Mechanics with Further Results in Equilibrium Charge Distributions

It is common in mesoscopic systems to find instances where several charges interact among themselves. These particles are usually confined by an external potential that shapes the symmetry of the equilibrium charge configuration. In the case of classical charges moving on a plane and repelling each other via the Coulomb potential, they possess a ground state à la Thomson or Wigner crystal. As the number of particles N increases, the number of local minima grows exponentially and direct or heuristic optimization methods become prohibitively costly. Therefore the only feasible approximation to the problem is to treat the system in the continuum limit. Since the underlying framework is provided by potential theory, we shall by-pass the corresponding mathematical formalism and list the most common cases found in the literature. Then we prove a (albeit known) mathematical correspondence that will enable us to re-discover analytical results in electrostatics. In doing so, we shall provide different methods for finding the equilibrium surface density of charges, analytical and numerical. Additionally, new systems of confined charges in three-dimensional surfaces will be under scrutiny. Finally, we shall highlight exact results regarding a modified power-law Coulomb potential in the d-dimensional ball, thus generalizing the existing literature.     

The locality problem in quantum measurements

The locality problem of quantum measurements is considered in the framework of the algebraic approach. It is shown that contrary to the currently widespread opinion one can reconcile the mathematical formalism of the quantum theory with the assumption of the existence of a local physical reality determining the results of local measurements. The key quantum experiments: double-slit experiment on electron scattering, Wheeler’s delayed-choice experiment, the Einstein-Podolsky-Rosen paradox, and quantum teleportation are discussed from the locality-problem point of view. A clear physical interpretation for these experiments, which does not contradict the classical ideas, is given.     

Why Gauge?

The world appears to be well described by gauge theories; why? I suggest that gauge is more than mathematical redundancy. Gauge-dependent quantities can not be predicted, but there is a sense in which they can be measured. They describe “handles” though which systems couple: they represent real relational structures to which the experimentalist has access in measurement by supplying one of the relata in the measurement procedure itself. This observation leads to a physical interpretation for the ubiquity of gauge: it is a consequence of a relational structure of physical quantities.     

Storming a Citadel: Mathematical Theory and Experimental Practice

Based upon a comparison of the viscosity experiments of James Clerk Maxwell (1831–1879) and Oskar Emil Meyer (1834–1909) in the 1860s, I argue that mathematical theory plays a significant role in both aspects of experimental practice, the design and construction of an experimental apparatus and the transformation of the observed experimental data into the value of a physical quantity. I argue further that Maxwell’s and Meyer’s evaluation of each other’s theoretical and experimental work depended significantly on the mathematical tools they employed in their theories.     

Characterization of phase transition in liquid crystals by voltaic potential difference

Our investigations show that the determination of voltaic potential differences is a useful method to characterize the phase transition N → I and I → N for a liquid-crystal (LC) mixture and for a phase transition from one liquid-crystalline phase into another. The ΔV/T curves show reversible as well as an irreversible behaviour. Moreover, the transition from the smectic into the nematic phase is demonstrated on liquid-crystalline polymers.     

金属薄膜制备及物性测量系列实验

介绍了由模拟真空实验和“金属薄膜的制备”、“金属薄膜厚度的测量”、“金属薄膜电阻率的测量”,以及“金属薄膜生长过程的动态监测”等4个实验组成的金属薄膜制备与物性测量系列实验.这组实验与现代科学技术发展联系紧密,仪器设备可靠,操作简单,适合于普通物理实验阶段的研究性教学.     

外形分析-拟合求导法测接触角

在外界来流作用下,液滴在固体表面上呈现周期性振荡特性,接触角的动态变化是表征该过程特性的重要参数, 传统方法不适用此接触角测量。在分析常用接触角测量方法的基础上,提出外形分析-拟合求导法测量动态接触角,同经典测量方法对比表明,外形分析-拟合求导法可很好地满足测量精度要求。     

Adhesion between an elastic body and a randomly rough hard surface

I have developed a theory of adhesion between an elastic solid and a hard randomly rough substrate. The theory takes into account that partial contact may occur between the solids on all length scales. I present numerical results for the case where the substrate surface is self-affine fractal. When the fractal dimension is close to 2, complete contact typically occurs in the macro-asperity contact areas, while when the fractal dimension is larger than 2.5, the area of (apparent) contact decreases continuously when the magnification is increased. An important result is that even when the surface roughness is so high that no adhesion can be detected in a pull-off experiment, the area of real contact (when adhesion is included) may still be several times larger than when the adhesion is neglected. Since it is the area of real contact which determines the sliding friction force, the adhesion interaction may strongly affect the friction force even when no adhesion can be detected in a pull-off experiment. Received 3 April 2002     

双麦克斯韦分布等离子体对航天器表面的充电效应

空间等离子体在有些情形下,并非单麦克斯韦分布,而是双麦克斯韦分布。为了研究双麦克斯韦分布等离子体对航天器表面的充电效应,基于等离子体动理学理论,建立表面充电平衡方程,综合考虑双麦克斯韦分布等离子体的粒子参数、航天器的单位电容、二次电子发射及光照等因素,得出了双麦克斯韦分布等离子体对航天器表面充电电位的计算表达式,给出了表面充电电位随时间的变化规律。研究结果表明:当等离子体为双麦克斯韦分布时,航天器表面充电电位低于单麦克斯韦分布等离子体环境下的表面充电电位,单麦克斯韦分布的等离子体假设会过高估计航天器表面的充电效应;双麦克斯韦分布的第二分布函数中,对最终的表面充电平衡电位影响较大的主要是离子成分;双麦克斯韦分布等离子体的粒子数密度或温度越高,则表面充电达到平衡所需的时间越长;单位电容仅影响表面充电电位达到稳定所需的时间,对最终的充电平衡电位值影响不大。     

Investigation of contact lithography in the 5–20 nm region with a laser plasma source

In this paper, we present experiments of extreme ultraviolet (EUV) contact lithography based on a compact laser-produced plasma (LPP) and investigated the radiation of the plasma from Cu, Fe, W targets. We measured the depth of development of a polychlorinated methylstyrene (PCMS) resist exposed through a 100 I mm⁻¹ Cu net for times ranging from 10 to 40 minutes using different targets.     

The physics of the Einstein-Podolsky-Rosen paradox

The Einstein-Podolsky-Rosen paradox as formulated in their original paper is critically examined. Their argument that quantum mechanics is incomplete is shown to be unsatisfactory on two important grounds. (i) The gedanken experiment proposed by Einstein, Podolsky, and Rosen is physically unrealizable, and consequently their argument is invalid as it stands. (ii) The basic assumptions of their argument are equivalent to the assumption that quantum mechanical systems are in fact describable by unique eigenfunctions of the operators corresponding to physical observables, independent of any observation or measurement. Following an argument due to Furry, it is shown that this interpretation of quantum mechanics must lead to some physical predictions at variance with those of conventional quantum mechanics. A decisive experiment has been performed by Freedman and Clauser, which rules out this interpretation, and imposes severe restrictions on any alternative theory which incorporates the Einstein, Podolsky, and Rosen concept of physical reality.     

清华大学汤姆逊散射超短脉冲X射线源研究

 介绍了清华大学加速器实验室近年来关于汤姆逊散射超短X射线源的研究工作;研究了在任意散射角度下电子束参数和激光束参数对散射光子参数的影响,给出了散射光子的参数如光子产额、脉冲长度、时间抖动等与电子束参数、激光束参数和散射角度的关系;利用实验室已有的16 MeV反波行波加速器与中国工程物理研究院激光聚变研究中心提供的ns调Q激光搭建了汤姆逊散射初步实验平台并开展了实验研究;加工了1.6-cell光阴极微波电子枪,搭建了高功率实验平台,对产生的电子束参数进行了初步测量;对汤姆逊散射超短X射线源进行了设计并开展了相关的平台建设工作,对产生的X射线脉冲参数进行了模拟。     

Photon-mass bound destroyed by vortices

The Particle Data Group gives an upper bound on the photon mass m < 2 x 10(-16) eV from a laboratory experiment and lists, but does not adopt, an astronomical bound m < 3 x 10(-27) eV, both of which are based on the plausible assumption of large galactic vector potential. We argue that the interpretations of these experiments should be changed, which alters significantly the bounds on m. If m arises from a Higgs effect, both limits are invalid because the Proca vector potential of the galactic magnetic field may be neutralized by vortices giving a large-scale magnetic field that is effectively Maxwellian. If, on the other hand, the galactic magnetic field is in the Proca regime, the very existence of the observed large-scale magnetic field gives m(-1) > or = 1 kpc, or m < or = 10(-26) eV.     

用差动放大器测量低电阻

根据伏安法测量电阻的优点以及电压跟随器和差动放大器的特点,提出了在低电阻测量中能消除导线电阻和接触电阻影响的一种新方法。设计了完整的实验电路,经过实际测量证明了该方法是可行的。     

Mathematical and physical aspects of controlling the exact solutions of the 3D Gross-Pitaevskii equation

The possibility of the decomposition of the three-dimensional (3D) Gross-Pitaevskii equation (GPE) into a pair of coupled Schrödinger-type equations, is investigated. It is shown that, under suitable mathematical conditions, it is possible to construct the exact controlled solutions of the 3D GPE from the solutions of a linear 2D Schrödinger equation coupled with a 1D nonlinear Schrödinger equation (the transverse and longitudinal components of the GPE, respectively). The coupling between these two equations is the functional of the transverse and the longitudinal profiles. The applied method of nonlinear decomposition, called the controlling potential method (CPM), yields the full 3D solution in the form of the product of the solutions of the transverse and longitudinal components of the GPE. It is shown that the CPM constitutes a variational principle and sets up a condition on the controlling potential well. Its physical interpretation is given in terms of the minimization of the (energy) effects introduced by the control. The method is applied to the case of a parabolic external potential to construct analytically an exact BEC state in the form of a bright soliton, for which the quantitative comparison between the external and controlling potentials is presented.