时间究竟是什么

物理学家们对于时间是什么有越来越多的争论,几十年来,他们试图将描述非常小的事物如何行事的量子力学理论与描述空间、时间和物质之间相互作用的广义相对论结合起来形成一个能描述整个宇宙的量子引力理论,加拿大佩里米特学院的理论物理学家斯莫林(L.Smolin)说:由于在广义相对论和量子理论中对于时间有迥异的概念,故如何在量子引力理论中协调时间的概念就成了一大难题.     

"引力"七问

1 引力是什么 牛顿在17世纪就认识到宇宙中任何地方的一切物体的引力作用方式是相同的,且两物体间的吸引力与它们的质量的乘积成比例,与它们距离的平方成反比,即著名的"引力的平方反比律."爱因斯坦在20世纪初发表的广义相对论是研究物质在空间和时间中如何进行引力相互作用的理论,它将平方反比律解释成时空因物质和能量的存在而发生畸变的结果,并把牛顿理论包含在内.     

引力的"磁性"是怎么回事

爱因斯坦广义相对论的重要结论之一是引力也应有“磁”分量，两个旋转物体之间会有引力“磁”矩的相互作用．而按牛顿引力论，两个物体的引力只决定于二者的质量，并不与二者旋转运动方向有关．因此，检验是否存在引力“磁”分量，乃成为区别牛顿引力论与广义相对论的关键之一．检验的方法是利用旋转物体，例如，在空间放置一个陀螺，按牛顿理论。     

广义相对论经改进可以拟合星系旋转曲线

引力虽然是我们最早认识到的力，爱因斯坦的引力理论在太阳系之外的弱场环境里是否适用，仍然没能被天文观测肯定．困扰天文学家大半个世纪的星系旋转曲线和暗物质问题就是众所周知的一个例子．2004年，以色列物理学家Bek-enstein提出一种新的TeVeS理论，把Milgrom1983年的MOND经验公式融合到修改或延伸后的广义相对论．最近，英国StAndrews大学的赵红胜博士和比利时布鲁塞尔ULB大学的BenoitFamaey发现用一个简单的TeVeS引力的修正公式，可以不用暗物质但很好地拟合绝大多数星系的旋转曲线．     

《爱因斯坦的宇宙》简介

《爱因斯坦的宇宙》是徐一鸿在《可畏的对称》成为畅销书之后的又一部科普著作．徐一鸿教授出生在上海，后来移民到巴西，又到美国求学．徐一鸿是理论物理研究所的永久成员，加利福尼亚大学圣巴巴拉校园物理系教授，是一位优秀的科普作家．他所著作品除本书外，还有《可畏的对称》、《吞云》和《力的统一》等书．本书的译者张礼     

量子引力和弦论在中国

直到20世纪60年代,爱因斯坦的广义相对论一直是理论物理中理论色彩最浓的一个分支,那时广义相对论的主要实验验证是水星近日点进动、太阳引力场中的光线弯曲、引力红移。直到宇宙学和涉及强引力场的一些天体物理问题成为实验观测对象后,广义相对论才成为和其他物理理论（如粒子物理）类似的学科。与此同时,人们开始尝试将引力和量子力学结合起来,这就是著名的量子引力或引力量子化问题。     

爱因斯坦:试图统一电磁力和引力未能如愿(Ⅰ)

在牛顿统一了天上力和地上力、麦克斯韦尔统一了电力和磁力之后,电力的库仑公式和磁力的安培公式与牛顿万有引力公式在数学形式上的相似,使人很容易联想到电磁力与引力的统一。爱因斯坦,在1905年创立狭义相对论、1915年创立广义相对论分别改进和完善了麦克斯韦电磁理论和牛顿引力理论之后,试图统一电磁力和引力,花费了后半生近30年的时光去建立统一场论,但至死未能如愿。本讲,我们先介绍爱因斯坦生平;然后介绍他的成功之作:狭义和广义相对论;最后介绍未能完成的统一场论。     

探求牛顿引力常数的精确值

<正>引力在物理学中具有举足轻重的位置。对于初学者,这仅仅是一种不能用量子理论描述的基本相互作用。然而,引力的普遍理论——牛顿定律和爱因斯坦广义相对论——将空间与时间视为连续的经典物理量,这些理论在守恒量子基础上描述电磁力与核力。另外,与其他基本作用力相比,引力作用非常弱,仅仅当能量     

伟大的物理学家--爱因斯坦

本文简单论述爱因斯坦的科学贡献、科学方法、哲学思想及其伟大人格，重点讨论爱因斯坦开创的通过修正公理发展物理学理论的方法．这一方法可以使我们“复制”一些物理定律，同时产生一套新的概念及其定义．情之所致，行文之中我们对爱因斯坦的伟大人格表述了由衷的赞叹。     

超弦理论纵横谈

 物理学有某种最终理论吗?终有一天,我们会有一个完整的理论,能对从微观的亚原子粒子、原子,到宏观的超新星,直至大爆炸的所有事物均作出国满的解释吗?爱因斯坦耗费了他一生中最后30年的宝贵时光.     

大学物理理论课与实验课的现状 问题与整合

针对目前高校物理教学的现状和问题,结合对本校现状的调查,分析了理论课与实验课脱节等问题的成因,并提出了相应的整合措施.     

There is No “Theory of Everything” Inside E8

We analyze certain subgroups of real and complex forms of the Lie group E₈, and deduce that any “Theory of Everything” obtained by embedding the gauge groups of gravity and the Standard Model into a real or complex form of E₈ lacks certain representation-theoretic properties required by physical reality. The arguments themselves amount to representation theory of Lie algebras in the spirit of Dynkin’s classic papers and are written for mathematicians.     

Alternative New Notation for Quantum Information Theory

The notation [Li, Song, and Luo (2002) Physics Letters A 297, 121] has been generalized to quantum information theory. By this notation,we present three useful criteria for bipartite entanglement, a formula for general quantum swapping, and a formula for quantum teleportation of bipartite state by two EPR pairs.     

Some New Features of Linear Theory for Describing Non-linear Diffusion

The non-linear flux equation, the non-linear Fokker-Planck equation (or Smoluchowski equation), and the non-linear Langiven equation are the basicequations for describing particle diffusion in non-ideal system subjected totime-dependent external fields. Nevertheless, the exact solution of thoseequations is still a challenge because of their inherent complexity of thenon-linear mathematics. Li et al. found that, based on the defined apparentvariables, the non-linear Fokker-Planck equation and the non-linear flux equation could be transformed to linear forms under the condition of strong friction limit or local equilibrium assumption. In this paper, some new features of the theory were found: (i) The linear flux equation for describing non-linear diffusion can be obtained from the irreversible thermodynamic theory; (ii) The linear non-steady state diffusion equation for describing non-linear diffusion of the non-steady state, which was described by the non-linear Fokker-Planck equation, can be derived more consistently from the microscopic molecular statistical theory; (iii) In the theory, thenon-linear Langiven equation also bears a linear form; (iv) For some special cases, e.g. diffusion in a periodic total potential system, the local equilibrium assumption or the strong friction limit is not required in establishing the linear theory for describing non-linear diffusion, so the linear theory may be important in the study of Brown motor.     

Some New Features of Linear Theory for Describing Non-linear Diffusion

The non-linear flux equation, the non-linear Fokker-Planck equation （or Smoluchowski equation）, and the non-linear Langiven equation are the basic equations for describing particle diffusion in non-ideal system subjected to time-dependent external fields. Nevertheless, the exact solution of those equations is still a challenge because of their inherent complexity of the non-linear mathematics. Li et al. found that, based on the defined apparent variables, the nonlinear Fokker-Planck equation and the non-linear flux equation could be transformed to linear forms under the condition of strong friction limit or loeal equilibrium assumption. In this paper, some new features of the theory were found： （i） The linear flux equation for describing non-linear diffusion can be obtained from the irreversible thermodynamic theory; （ii） The linear non-steady state diffusion equation for describing non-linear diffusion of the non-steady state, which was described by the non-linear Fokker-Planek equation, can be derived more consistently from the microscopic molecular statistical theory; （iii） In the theory, the non-linear Langiven equation also bears a linear form; （iv） For some special cases, e.g. diffusion in a periodic total potential system, the local equilibrium assumption or the strong friction limit is not required in establishing the linear theory for describing non-linear diffusion, so the linear theory may be important in the study of Brown motor.     

A New Cohomology Theory of Orbifold

Based on the orbifold string theory model in physics, we construct a new cohomology ring for any almost complex orbifold. The key theorem is the associativity of this new ring. Some examples are computed.Both authors partially supported by the National Science Foundation     

Some New Solutions Derived From the 5-Dimensional Theory—The New Methods of Creating Solutions

Application of the 5-dimensional coordinate transformations in the 5-dimensional theory lead us to some new solutions for the 4-dimensional Einstein–Maxwell equations and the relevant scaler equation. From the Kerr solution we derive the corresponding solution. And we propose a new method to solve the usual 4-dimensional Einstein–Maxwell equations and the scalar equation, illustrating by three examples.     

Exploring Spectroscopic and Physicochemical Properties of New Fluorescent Ionic Liquids

In the current study, spectroscopic and physicochemical properties of newly prepared ionic liquids were investigated. Ionic liquids were synthesized via a simple and straightforward route using a metathesis reaction of either N,N-diethyl-p-phenylenediamine monohydrochloride or N-phenacylpyridinium bromide with bis(trifluoromethane)sulfonimide lithium in water. High yield and purity were obtained for the resultant ionic liquids. Data acquired by use of ¹H NMR and FT-IR measurements were consistent with the chemical structures of newly prepared ionic liquids. Results of thermal gravimetric analysis also implied that these ionic liquids have good thermal stability. In addition, UV–vis and fluorescence spectroscopy measurements provided that new ionic liquids are good absorbent and fluorescent. Time-based fluorescence steady-state measurements showed that ionic liquids have high photostability against photobleaching. For a deeper mechanistic understanding of the analytical potential of newly synthesized ionic liquids, spectroscopic and physicochemical parameters, including singlet absorption, extinction coefficient, fluorescence quantum yield, Stokes shift, oscillator strength and dipole moment, were also investigated.     

探究汞灯测量透明薄片厚度的新方法

本文介绍了一种利用汞灯的干涉现象来测量透明薄片厚度的新方法.