I have derived these pair of coupled diff equations for [itex]U_1 (r)[/itex] and [itex]U_2 (r)[/itex]:(adsbygoogle = window.adsbygoogle || []).push({});

[itex]r^2 \dfrac{d^2 U_1 (r)}{dr^2} + r \dfrac{d U_1 (r)}{dr} + r^2 U_2(r) = 0[/itex]

and

[itex]r^2 \dfrac{d^2 U_2 (r)}{dr^2} + r \dfrac{d U_2 (r)}{dr} - r^2 U_1(r) = 0[/itex]

Or written in matrix form

[itex](r^2 \dfrac{d^2}{dr^2} + r \dfrac{d}{dr}) \begin{pmatrix} U_1(r) \\ U_2(r) \end{pmatrix} + r^2 \begin{pmatrix} 0 & 1 \\ -1 & 0 \end{pmatrix} \begin{pmatrix} U_1(r) \\ U_2(r) \end{pmatrix} = 0[/itex]

I've tried a couple of things to try to solve them but didn't work. Any tips appreciated! Probably going to involve zeroth-order Bessel / modified Bessel functions? Thanks.

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# Coupled 2nd order diff eq's (Bessel functions?)

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