We extend the discussion on the difference between angular momentum and pseudo-angular momentum in field theory. We show that the often quoted expressions in [Phys.Rev.B 103, L100409 (2021)] only apply to a non-linear system, and derive the correct rotation symmetry and the corresponding angular momentum for a linear elastic system governed by Navier-Cauchy equation. By mapping the concepts and methods for the elastic wave into electromagnetic theory, we argue that the renowned canonical and Benlinfante angular momentum of light are actually pseudo-angular momentum. Then, we derive the ``Newtonian" momentum $\int \text{d}^3 x\boldsymbol{E}$ and angular momentum $\int \text{d}^3 x (\boldsymbol{r}\times\boldsymbol{E})$ for a free electromagnetic wave, which are conserved quantities during propagation in vacuum.
Gauge theory requires physical observables to be gauge-independent. However, ever since Lamb noticed the problem of gauge selection in calculating atomic spontaneous radiation spectrum, the problem of gauge dependence was encountered in many fields of physics research. Therefore, it is important to test the self-consistency of gauge symmetry for various physical systems. In this paper, we calculate the transient spontaneous radiation spectrum of a relativistic hydrogen atom in the non-uniform electrostatic field under the atomic self-reference frame. The physical system studied in this paper is a frame-transformed version of our recent work [\href{https://link.springer.com/paper/10.1140/epjd/s10053-022-00407-5}{Euro. J. Phys. D \textbf{76}, 84(2022)}] where the radiating object is static while the charge is moving relativistically. The obtained peak frequency can differ by about $413$ $\mathrm{KHz}$ or larger for the commonly used Coulomb, Lorentz, and multipolar gauges. This observation can be significant not only for studying how the gauge field interacts with the quantum system in theory, but also for practical experimental applications, such as the timing accuracy of atomic clocks in the external electromagnetic field.
运用AHP-熵值法、修正引力模型及社会网络分析法,以镇域为研究单元,以"点-线-面"的思路对新沂市城镇空间结构进行优化研究.结果表明:(1)县域高质量发展空间不平衡性突出,极化现象明显,高质量主要体现在经济发展水平、人民生活水平与城乡建设水平3个方面;(2)城镇联系呈现明显的地缘偏向和层次差异,并体现出"东西向密、南北向疏"的特征,联系方向主要表现出"中心城镇指向性"与"临近城镇指向性"的特点;(3)网络子群边界清晰,均衡性较差.建议将城镇体系优化为"1+3+3+7"结构,空间结构优化为"一心+三轴线+五组团"发展模式.
为了完善与扩展数字化的政务服务和政务治理体系理论,以政务数据治理理论为基础,以数字政府中的数据共享与数字服务,特别是跨源多维政务数据为研究对象,构建电子政务数据共享与服务创新的理论和方法,提出一种基于区块链的跨源多维政务数据治理模型.该模型从政务数据结构、服务制度、应用模式3个方面融合架构,结合区块链技术,以数字政府的服务创新为目标,实现了数字经济下的跨源多维政务业务数据治理.同时为了解决跨源多维政务数据共享服务质量的问题,提出2种服务创新方法,最后验证跨源多维政务数据共享服务应用成效,借鉴基于超效率 DEA评价的政务资源服务效率的评价方法,可以验证数据治理模型的阶段绩效,对各部门跨源多维政务数据共享信息化服务进行绩效评价.该政务数据治理模型在实践中持续完善与改进,为实践应用的路径探索、城市治理与服务创新提供参考.
