On the status of the geodesic principle in Newtonian and relativistic physics

A theorem due to Geroch and Jang (1975) provides a sense in which the geodesic principle has the status of a theorem in General Relativity. I have recently shown that a similar theorem holds in the context of geometrized Newtonian gravitation (Newton–Cartan theory) (Weatherall, J.O., 2011). Here I compare the interpretations of these two theorems. I argue that despite some apparent differences between the theorems, the status of the geodesic principle in geometrized Newtonian gravitation is, mutatis mutandis, strikingly similar to the relativistic case.     

公路勘测设计的CAI软件设计

公路勘测设计是交通工程专业学生的必修课，具有较强的实践性。传统的封闭式教学模式虽可系统传授理论知识，但在培养学生设计能力方面却有较大的局限性。为突破这一局限，公路勘测设计CAI软件利用计算机强大的计算和绘图功能，以及处理交互信息的独特优势，对公路设计的实际过程进行模拟及演示，较为详细地介绍了公路勘测设计CAI软件的总体设计方案，系统的核心模块-模拟设计模块，数据流图，以及软件开发所使用的编程语言。     

刑罚目的的双重身份及其基础上的合理构建

刑罚目的既是国家制定、适用和执行刑罚所要达到的目的,又是国家用以指导刑罚制定、适用和执行的手段,因此刑罚目的同时具有目的和手段的双重身份。本文从刑法目的的两种不同身份出发,进行分析论证,得出了我国刑法目的应该是特殊预防这一结论。     

体操运动员的一般心理训练

利用一般心理训练来提高体操运动员的运动技术水平，达到理论和实践相结合的效果，更有利于运动竞技水平的提高，取得最佳成绩。     

普通生物学实践教学初探

从本校实际出发,结合自己的教学实践,对普通生物学实践教学不断改进,力求培养学生的实践和创新能力。     

Einstein׳s Equations for Spin 2 Mass 0 from Noether׳s Converse Hilbertian Assertion

An overlap between the general relativist and particle physicist views of Einstein gravity is uncovered. Noether׳s 1918 paper developed Hilbert׳s and Klein׳s reflections on the conservation laws. Energy-momentum is just a term proportional to the field equations and a ‘curl’ term with identically zero divergence. Noether proved a converse “Hilbertian assertion”: such “improper” conservation laws imply a generally covariant action.Later and independently, particle physicists derived the nonlinear Einstein equations assuming the absence of negative-energy degrees of freedom (“ghosts”) for stability, along with universal coupling: all energy-momentum including gravity׳s serves as a source for gravity. Those assumptions (all but) imply (for 0 graviton mass) that the energy-momentum is only a term proportional to the field equations and a symmetric “curl,” which implies the coalescence of the flat background geometry and the gravitational potential into an effective curved geometry. The flat metric, though useful in Rosenfeld׳s stress-energy definition, disappears from the field equations. Thus the particle physics derivation uses a reinvented Noetherian converse Hilbertian assertion in Rosenfeld-tinged form.The Rosenfeld stress-energy is identically the canonical stress-energy plus a Belinfante curl and terms proportional to the field equations, so the flat metric is only a convenient mathematical trick without ontological commitment. Neither generalized relativity of motion, nor the identity of gravity and inertia, nor substantive general covariance is assumed. The more compelling criterion of lacking ghosts yields substantive general covariance as an output. Hence the particle physics derivation, though logically impressive, is neither as novel nor as ontologically laden as it has seemed.     

普通物理教学中培养学生创新能力之探讨

普通物理学是理工类专业的一门重要专业基础课。如何提高普通物理学的教学质量、培养出富有创新能力和实践能力的高素质人才,是摆在高校教师面前的一个重要课题。本文结合作者教学实践经验,从教学内容、教学方法、评价机制等几个环节入手,探讨了学生创新能力与实践能力的培养。     

广义位移控制法在动力稳定问题中的应用

利用线性加速度假定消去结构非线性动力平衡方程中的微分项．在动力平衡路径跟踪过程中，以比例加载的形式，对所有荷载分量进行同步动态调整，考虑到强非线性结构在临界屈曲状态时可能有多个临界点和平衡路径可能反跳，而引入广义刚度参数对荷载参数增量的步长和符号进行自动控制，并通过广义刚度参数对结构的动力稳定性进行判定．通过算例分析验证了这一算法的有效性.     

求解广义变分不等式问题算法的一个注

对Noor MA (1999)给出的求解广义变分不等式问题的外梯度求解算法，给出一个反例，说明该算法无效。     

爱因斯坦相对论的根本性修正——光速可变的相对论力学(下)

本文从多方面证明爱因斯坦的光速不变假设和洛伦兹的长度收缩假设不成立,基于这两个假设的洛伦兹变换不能赋予麦克斯威电磁场方程及电磁波方程以不变性,不能解释多普勒效应和先行差,不能给出动体的质能当量关系,爱因斯坦力学的动质量公式与动能公式不自洽.他的广义相对论不能解释水星近日点进动.作者立足于相对性原理,不需要其他任何假设,建立了新的相对论.新理论证明:同时性是普适的;光速可变,光速不是速度的极限;多普勒效应、红移和光行差都是光速变化引起的;光子有静质量.新理论还能精确地证明动体的质能当量关系及惯性质量与引力质量等效,并揭示惯性场与引力场的广义对应.新的相对论力学可以准确计算光线经过太阳表面的偏转及水星近日点进动.从而用力学诠释取代了爱因斯坦关于质量使时空扭曲的几何诠释,并消除了他的广义相对论与狭义相对论之间的矛盾.