New class of solutions to Laplace equation: Regularized multipoles of negative orders

We introduce a new class of solutions to the Laplace equation, dubbed logopoles, and use them to derive a new relation between solutions in prolate spheroidal and spherical coordinates. The main novelty is that it involves spherical harmonics of the second kind, which have rarely been considered in...

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Main Authors: Matt Majic, Eric C. Le Ru
Format: Article
Language:English
Published: American Physical Society 2019-12-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.1.033213
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author Matt Majic
Eric C. Le Ru
author_facet Matt Majic
Eric C. Le Ru
author_sort Matt Majic
collection DOAJ
description We introduce a new class of solutions to the Laplace equation, dubbed logopoles, and use them to derive a new relation between solutions in prolate spheroidal and spherical coordinates. The main novelty is that it involves spherical harmonics of the second kind, which have rarely been considered in physical problems because they are singular on the entire z axis. Logopoles, in contrast, have a finite line singularity like solid spheroidal harmonics, but are also closely related to solid spherical harmonics and can be viewed as an extension of the standard multipole ladder toward the negative multipolar orders. As part of our derivations, we also found a new integral representation for the spherical harmonics of the second kind in terms of their source distributions. As an example application, we use logopoles to construct a fast converging series solution for the problem of a point charge interaction with a dielectric sphere, which extends the basic image approximations introduced by Kelvin, Kirkwood, and Friedman. We believe these new solutions will prove a fruitful alternative to either spherical or spheroidal harmonics in a wide range of other physical problems.
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spelling doaj.art-491eae2e660f4a4a89875a5c68bfb8032024-04-12T16:48:06ZengAmerican Physical SocietyPhysical Review Research2643-15642019-12-011303321310.1103/PhysRevResearch.1.033213New class of solutions to Laplace equation: Regularized multipoles of negative ordersMatt MajicEric C. Le RuWe introduce a new class of solutions to the Laplace equation, dubbed logopoles, and use them to derive a new relation between solutions in prolate spheroidal and spherical coordinates. The main novelty is that it involves spherical harmonics of the second kind, which have rarely been considered in physical problems because they are singular on the entire z axis. Logopoles, in contrast, have a finite line singularity like solid spheroidal harmonics, but are also closely related to solid spherical harmonics and can be viewed as an extension of the standard multipole ladder toward the negative multipolar orders. As part of our derivations, we also found a new integral representation for the spherical harmonics of the second kind in terms of their source distributions. As an example application, we use logopoles to construct a fast converging series solution for the problem of a point charge interaction with a dielectric sphere, which extends the basic image approximations introduced by Kelvin, Kirkwood, and Friedman. We believe these new solutions will prove a fruitful alternative to either spherical or spheroidal harmonics in a wide range of other physical problems.http://doi.org/10.1103/PhysRevResearch.1.033213
spellingShingle Matt Majic
Eric C. Le Ru
New class of solutions to Laplace equation: Regularized multipoles of negative orders
Physical Review Research
title New class of solutions to Laplace equation: Regularized multipoles of negative orders
title_full New class of solutions to Laplace equation: Regularized multipoles of negative orders
title_fullStr New class of solutions to Laplace equation: Regularized multipoles of negative orders
title_full_unstemmed New class of solutions to Laplace equation: Regularized multipoles of negative orders
title_short New class of solutions to Laplace equation: Regularized multipoles of negative orders
title_sort new class of solutions to laplace equation regularized multipoles of negative orders
url http://doi.org/10.1103/PhysRevResearch.1.033213
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