一种多功能的角动量定理演示仪

介绍了一种用于课堂的多功能角动量定理演示仪,结构简单,操作方便,能演示出多种角动量定理相关实验,揭示刚体定点转动中深刻的物理规律,并采用在"自然坐标系"下的角动量定理对实验现象加以理论分析.     

傅里叶变换基本性质的物理诠释

数学物理方法是物理学专业基础课,其中的积分变换部分也是工程技术专业的基本教学内容.在该课程中,傅里叶变换往往是积分变换法教学的首要内容,而傅里叶变换的基本性质则是该部分的重点,也是其产生广泛应用的关键原因.本文从振动的合成与分解、物理学量纲分析等角度对傅里叶变换的线性定理、延迟定理、位移定理、标度变换定理、微分定理及卷积定理共6条基本性质进行了物理学诠释.对学生深刻理解和灵活运用傅里叶变换法解决物理问题、进行信号频谱分析大有裨益;对学生学习后续的量子力学、信号与系统等课程亦有帮助.     

矢量场类比法在电磁学教学中的应用探讨

电磁学是物理学的重要分支,但是学生总觉得这部分知识很难学,对于高斯定理和环路定理的理解也比较模糊.本文推广矢量场类比法,将矢量场类比为流体中的流速场,用水的流量类比为通量,流速沿环路的分量类比为环量.通过研究流体中的"起点"和"终点",类比为矢量场中"源"和"汇",用流体里的"漩涡"类比矢量场的"涡旋",并引出高斯定理和环路定理,让学生理解这些定理背后的物理含义.这种方法对后续学习电场强度通量、磁感应强度通量、电场线和磁感应线都有帮助,也有助于理解电场"有源无旋"和磁场"有旋无源"的性质.     

特勒根定理的证明及应用

本文用回路电流法证明了特勒根定理，并用该定理证明了弥尔曼定理和互易定理。     

《相对论、宇宙与时空》连载⑧——相对论预言的天体(黑洞)(下)

5 黑洞热力学 人们认为激发态的黑洞具有生命力,而基态的黑洞则是一颗死亡的星,是恒星演化的最后归宿.基态的史瓦西黑洞除去能不断吞食物质外,不会再有任何物理过程.然而,这个认识很快就被推翻了,基态的黑洞,实际上也是一颗充满生命力的活跃的星.我们先看一下黑洞的"无毛定理"和"面积定理"[3-14].     

生命学科"大学物理"教学中的几点想法

生命科学和物理科学日益融汇贯通,在"大学物理"教学中将物理知识和生命科学的问题相结合很有必要.文中重点谈了在"大学物理"教学中能量均分定理以及熵和自由能在生命科学领域的延伸.     

带电细圆环与导体球壳系统的场分布

先依电象法,推导均匀带电圆环在金属导体球壳内的"象电荷";再在球坐标系下,根据电场强度的计算公式与Tay-lor展开式,计算出均匀带电细圆环在全空间的电场分布的级数形式解;进而结合唯一性定理和电场的叠加原理,获得带电细圆环与导体球壳系统的空间场分布.     

平面上方二维介质目标对高斯波束的电磁散射研究

基于矩量法、互易性定理及镜像理论,提出了一种新的混合方法用于研究水平分界面上方二维介质目标对垂直入射高斯波束的差值散射场.应用镜像理论,介质水平分界面可被原始目标相对于该分界面的镜像目标所替代,从而给出散射问题的等效模型.在等效模型中,应用矩量法求解了原始目标及镜像目标对高斯波束的散射场,同时结合互易性定理得到了原目标与其镜像目标之间的耦合散射场.数值计算结果与相关文献方法及MoM所得结果进行了比较,验证了该混合方法的有效性. 关键词： 互易性定理 电磁散射 高斯波束 二维目标     

用复势函数法计算共焦椭圆柱形电缆的磁场

运用复势函数法通过选取余弦函数,再根据磁场强度复数公式并结合安培环路定理计算出共焦椭圆形电缆的内外磁场.     

基于多元局部多项式方法的混沌时间序列预测

根据Takens定理，把混沌时间序列构造为一组序列对，然后用多元局部多项式方法来预测其序列.这种核估计方法可以结合局域法与全局法的优点，使得预测的精度更高.仿真结果表明，该方法非常有效.     

留数定理在拓扑相变中的应用

留数定理是高校物理专业必修课程数学物理方法中的一个重要定理.传统教学中关于该定理的讲授着重于数学公式的推导和数学思想的传达,而对于其在具体物理问题上的应用鲜有涉及.本文以一维Su-Schrieffer-Heeger模型的拓扑相变问题为例,阐明了如何利用留数定理解析得到二阶位移量的表达式并用该物理量表征拓扑相变.在讲授留数定理的教学过程中引入具体物理问题的分析实例,可以使学生更深刻地理解数学定理中的物理内涵.     

莫比乌斯变换及其物理应用

北京科技大学陈难先教授把数论中的一条古老定理:莫比乌斯变换推广到普通函数并创造性地用之于物理学中许多反问题,取得了巨大成功。在此以更直观和易于理解的方式导出陈氏定理,并通过一些具体实例展示其应用前景。     

Who Proved Haag's Theorem?

In physics literature, there are several different characterizations of Haag's theorem and its consequences for quantum field theory. These different versions of Haag's theorem are due in part to various generalizations and more “rigorous” proofs of Haag's theorem as well as to the fact that many of these proofs were done using different formulations of quantum field theory. As a result, there is confusion about what Haag's theorem is and when it was proved. This paper clears up some of these confusions by examining the history and development of Haag's theorem up to 1959. It is argued that the question of who proved Haag's theorem is tied up with what the theorem is taken to show.     

Probabilistics: A lost science

For certain methodological and historical reasons, the science of probability (probabilistics) had never been constructed before as a single whole, and it has basically split into probability theory and into statistics. One of the reasons was the neglect of an extremely important methodological principle which reads: It is necessary to distinguish strictly between concrete objects and abstract objects. This principle is displayed and exemplified. Its use has made it possible to discover the basic phenomenon of probalilistics and to construct the science, whose outlines are given. The application of probabilistics to physics gives rise to probabilistic physics, whose particular domains are, among others, both classical statistical physics and quantum physics. The actual meaning of quantum physics becomes quite clear and no artificial interpretation of it proves to be necessary.The paper is based on the talk given by the author at a joint mathematics-physics seminar at the University of Massachusetts (Amherst) on December 2, 1980.     

新高考改革对浙江学生物理学习态度的影响

本文通过科罗拉多物理学习态度问卷调查,发现新高考改革对浙江省学生的物理学习态度造成了很大的影响,学考、选考两组学生在各个维度的物理学习态度上都存在着很大的差异性.而"大学物理预修"课程的开展对改善这种差异性有一定的效果,并提高了学考学生的物理成绩,同时也加强了对学生物理思维的训练,在一定程度上抵消了新高考改革带来的影响.     

Hydrodynamics and the fluctuation theorem

The fluctuation theorem is a pivotal result of statistical physics. It quantifies the probability of observing fluctuations which are in violation of the second law of thermodynamics. More specifically, it quantifies the ratio of the probabilities of observing entropy-producing and entropy-consuming fluctuations measured over a finite volume and time span in terms of the rate of entropy production in the system, the measurement volume, and time. We study the fluctuation theorem in computer simulations of planar shear flow. The simulations are performed by employing the method of multiparticle collision dynamics, which captures both thermal fluctuations and hydrodynamic interactions. The main outcome of our analysis is that the fluctuation theorem is verified at any averaging time provided that the measurement volume exhibits a specific dependence on a hydrodynamic time scale.     

Proof of factorization using background field method of QCD

Factorization theorem plays the central role at high energy colliders to study standard model and beyond standard model physics. The proof of factorization theorem is given by Collins, Soper and Sterman to all orders in perturbation theory by using diagrammatic approach. One might wonder if one can obtain the proof of factorization theorem through symmetry considerations at the lagrangian level. In this paper we provide such a proof.     

Noether's Theorem and the Conservation Laws of the KORTEWEG-DE VRIES Equation

A method developed recently by the author to derive a continuum of conservation laws by Noether's theorem from the so-called extended Bäcklund transformations is applied to the KORTEWEG -DE VRIES equation that describes various nonlinear dispersive wave phenomena in hydrodynamics, plasma physics and solid state physics. Further applications of Noether's theorem concerning this equation are given. It is shown that the Galilean transformation in the present case has an analogous function as Lie's transformation has with respect to the sine-Gordon equation.     

IMPROVEMENT OF THERMODYNAMICAL MONTE CARLO SIMULATION IN SU(2) PURE GAUGE FIELD THEORY ——AN APPROACH TO CONTINUUM PHYSICS LIMIT

The thermodynamical quantities of SU(2) pure lattice gauge field have been simulated first time on the asymmetric lattice (ξ>1).The finite size effect and continuum physics limits have also been studied.The results show that the use of asymmetric lattice is of benefit to calculate the thermodynamical quantities and study the behavior of continuum physics limits.In addition,it is explained that the efficiency of the whole Monte Carlo simulation and the calculation of heat capacity will be improved quite a lot by using bias sampling technique.