三体问题的受力分析--兼谈失重

分析了三体问题的受力规律,给出了失重的条件．     

由太阳引力矩引起的地-月系统角动量的变化

导出了地-月系统受到的太阳引力对其质心的引力矩,讨论了由引力矩引起的地-月系统角动量的变化,提出了对理论所预期的变化的观测验证方法。     

Modification of gravitational redshift of x-ray burst produced by pulsar surface magnetoplasma

In this paper, the propagation of x-ray bursts in the magnetoplasma of pulsar magnetosphere is discussed. The electromagnetic interaction between x-ray bursts and magnetoplasma is described as some geometry. The electromagnetic effects of surface superstrong magnetic field and dynamic effects of outflowing magnetoplasma of pulsars are treated as an optical metric. The Gordon metric is introduced to represent the gravitational metric and optical metric. So the propagation of x-ray bursts in magnetoplasma of pulsars can be described as x-ray bursts transmitting in an effective space characterized by Gordon metric. The modification of gravitational redshift, attributed to the flowing magnetoplasma of pulsars, is obtained and it is shown that the modification is of redshift and can reach the same magnitude as the gravitational redshift for ordinary pulsars.     

密立根油滴实验中一个不能忽视的小问题

本文分析了油滴从静止到匀速的过程,讨论了密立根油滴实验中油滴从静止开始下落到匀速直线运动状态所用的时间.在实验课的教学中给了学生关于加速弛豫过程时间量的概念,排除了测量过程中困扰学生的一个重要因素.     

Boundary conditions of the RGE flow in the noncommutative geometry approach to particle physics and cosmology

We investigate the effect of varying boundary conditions on the renormalization group flow in a recently developed noncommutative geometry model of particle physics and cosmology. We first show that there is a sensitive dependence on the initial conditions at unification, so that, varying a parameter even slightly can be shown to have drastic effects on the running of the model parameters. We compare the running in the case of the default and the maximal mixing conditions at unification. We then exhibit explicitly a particular choice of initial conditions at the unification scale, in the form of modified maximal mixing conditions, which have the property that they satisfy all the geometric constraints imposed by the noncommutative geometry of the model at unification, and at the same time, after running them down to lower energies with the renormalization group flow, they still agree in order of magnitude with the predictions at the electroweak scale.     

Higher Flavor Symmetries in the Standard Model

A study of the generalized global flavor symmetries of the Standard Model is initiated. The presence of nonzero triangle diagrams between the U(3)⁵ flavor currents and the $U{(1)}_Y$ hypercharge current intertwines them in the form of a higher-group which mixes the zero-form flavor symmetries with the one-form magnetic hypercharge symmetry. This higher symmetry structure greatly restricts the possible flavor symmetries that may remain unbroken in any ultraviolet completion that includes magnetic monopoles. In the context of unification, this implies tight constraints on the combinations of fermion species which may be joined into multiplets. Three of four elementary possibilities are reflected in the classic unification models of Georgi–Glashow, $SO(10)$, and Pati–Salam. The final pattern is realized non-trivially in trinification, which exhibits the sense in which Standard Model Yukawa couplings which violate these flavor symmetries may be thought of as spurions of the higher-group. Such modifications of the ultraviolet flavor symmetries are possible only if new vector-like matter is introduced with masses suppressed from the unification scale by the Yukawa couplings.