Electrodynamic spherical harmonic is a second rank tensor in three-dimensional space. It allows to separate the radial and angle variables in vector solutions of Maxwell's equations. Using the orthonormalization for electrodynamic spherical harmonic, a boundary problem on a sphere can be easily solved.
We derive new relationships expressing solid spherical harmonics as series of toroidal harmonics and vice versa. The expansions include regular and irregular spherical harmonics, ring and axial toroidal harmonics of even and odd parity about the plane of the torus. The expansion coefficients are given in terms of a recurrence relation. As an example application we apply one of the expansions to express the potential of a charged conducting torus on a basis of spherical harmonics.
We prove a Central Limit Theorem for the Critical Points of Random Spherical Harmonics, in the High-Energy Limit. The result is a consequence of a deeper characterizations of the total number of critical points, which are shown to be asymptotically fully correlated with the sample trispectrum, i.e., the integral of the fourth Hermite polynomial evaluated on the eigenfunctions themselves. As a consequence, the total number of critical points and the nodal length are fully correlated for random spherical harmonics, in the high-energy limit.
Laplace's equation for a point source near a sphere: improved internal solution using spheroidal harmonics
如最近所示[Phys. Rev. E 95,033307(2017)],球谐函数展开非常适合于球形物体外部点源的拉普拉斯方程的外部解。它们的内在奇异性与解的解析延拓的线奇异性相匹配,并且级数解比标准球谐解收敛得快得多。在这里,我们将这种方法扩展到内部电位使用开尔文变换,即径向反演,球坐标系。该变换将包含规则固体球谐函数的标准级数解转换为一系列不规则球谐函数。然后,我们取代的不规则球谐函数的扩展转换成潜在的不规则球谐函数。球谐解与解的像线奇异性拟合较好,收敛速度较快。我们还讨论了为什么解决方案中的定期固体球谐函数不能工作,即使这些功能是有限的,在球的任何地方。我们还提出了类似的解决方案,为内部点源,和两个新的关系之间的固体球谐函数和球谐函数。
Tensor harmonics are a useful mathematical tool for finding solutions to differential equations which transform under a particular representation of the rotation group $\mathrm{SO}(3)$. The aim of this work is to make use of this tool also in the setting of Finsler geometry, or more general geometries on the tangent bundle, where the objects of relevance are d-tensors on the tangent bundle, or tensors in a pullback bundle, instead of ordinary tensors. For this purpose, we construct a set of d-tensor harmonics for spherical symmetry and show how these can be used for calculations in Finsler geo…
Closed formulas in terms of double sums of Clebsch-Gordan coefficients are computed for the evaluation of bra-ket spherical harmonic overlap integrals of a wide class of trigonometric functions. These analytical expressions can find useful application in problems involving non-separable wave equations, e.g. general-relativistic perturbation theory, electromagnetism, quantum theory, etc, wherein the overlap integrals arise from the coupling among different angular modes.