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Regarding the Janzen-Rayleigh expansion, the formula given in the section was incorrect.
I checked physically and I ran simulations, it makes no sense to have a plus sign as it was :
I believe it is :. Therefore I changed it that way. — Preceding unsigned comment added by 2A01:CB08:189:DA00:AD69:8CA3:7B17:3888 (talk) 16:54, 4 April 2024 (UTC)[reply]
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![{\displaystyle \phi (r,\theta )=Ur\left(1+{\frac {a^{2}}{r^{2}}}\right)\cos \theta -\mathrm {M} ^{2}{\frac {Ur}{12}}\left[\left({\frac {13a^{2}}{r^{2}}}-{\frac {6a^{4}}{r^{4}}}+{\frac {a^{6}}{r^{6}}}\right)\cos \theta +\left({\frac {a^{4}}{r^{4}}}-{\frac {3a^{2}}{r^{2}}}\right)\cos 3\theta \right]+\mathrm {O} \left(\mathrm {M} ^{4}\right)\,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/a0df3449bfd8b1774402475ba348f36ec7ea1a13)
![{\displaystyle \phi (r,\theta )=Ur\left(1-{\frac {a^{2}}{r^{2}}}\right)\cos \theta -\mathrm {M} ^{2}{\frac {Ur}{12}}\left[\left({\frac {13a^{2}}{r^{2}}}-{\frac {6a^{4}}{r^{4}}}+{\frac {a^{6}}{r^{6}}}\right)\cos \theta +\left({\frac {a^{4}}{r^{4}}}-{\frac {3a^{2}}{r^{2}}}\right)\cos 3\theta \right]+\mathrm {O} \left(\mathrm {M} ^{4}\right)\,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e791a255fc96e001e0b24bc037c3e8199c004364)