In this article we study some classical aspects of Podolsky Electrodynamics in the static regime. We develop the multipole expansion for the theory in both the electrostatic and the magnetostatic cases. We also address the problem of consistently truncating the infinite series associated with the several kinds of multipoles, yielding approximations for the static Podolskian electromagnetic field to any degree of precision required. Moreover, we apply the general theory of multipole expansion to some specific physical problems. In those problems we identify the first terms of the series with the monopole, dipole and quadrupole terms in the generalized theory. We also propose a situation in which Podolsky theory can be experimentally tested.
Note on "Finite Field-Energy and Interparticle Potential in Logarithmic Electrodynamics"
我们提出了一个识别的自由参数的非线性电动力学模型中提出的P. Gaete和J. Helayel-Neto，Eur。Phys. J. C 74，2816（2014）通过将其拉格朗日函数的幂展开中的第二项与海森堡-欧拉拉格朗日函数的展开中的第二项等同起来。如果电荷是电子的电荷，则点状电荷的场能的结果值为电子质量的0.988。
Multipole Expansion of Gravitational Waves: from Harmonic to Bondi coordinates
我们将多极后闵可夫斯基近似中孤立物质源的度规从简谐（de Donder）坐标变换到辐射Newman-Unti（NU）坐标。为了线性化的顺序，我们得到的NU度规作为源的质量和电流多极矩的功能，有效的整个外部区域的源。施加适当的边界条件，我们恢复广义Bondi-van der Burg-Metzner-Sachs剩余对称群。对于二次阶，在质量-四极相互作用的情况下，我们确定了引力波尾在NU度规中的贡献，并证明了度规的半径展开对所有阶都是正则的.质量和角动量方面，以及邦迪剪切，从公制读出。它们由包括尾项的辐射四极矩给出。
