diff --git a/worknotes.lyx b/worknotes.lyx index ea19fc7..d01ae98 100644 --- a/worknotes.lyx +++ b/worknotes.lyx @@ -280,6 +280,105 @@ The expressions for are dimensionless. \end_layout +\begin_layout Standard + +\emph on +Note about the case +\begin_inset Formula $\theta\to0,\pi$ +\end_inset + +: +\emph default + There is a divergent +\begin_inset Formula $1/\sin\theta$ +\end_inset + + factor in the +\begin_inset Formula $\pi_{mn}(\cos\theta)$ +\end_inset + + function. + For +\begin_inset Formula $m=0$ +\end_inset + +, it is irrelevant because of the +\begin_inset Formula $m$ +\end_inset + + factor (it would be bad otherwise, because +\begin_inset Formula $P_{n}^{0}(\cos\theta)$ +\end_inset + + does not go to zero at +\begin_inset Formula $\theta\to0,\pi$ +\end_inset + +). + For +\begin_inset Formula $\left|m\right|\ge2$ +\end_inset + +, +\begin_inset Formula $P_{n}^{m}(x)$ +\end_inset + + behaves as +\begin_inset Formula $o(x+1),o(x-1)$ +\end_inset + + at +\begin_inset Formula $-1,1$ +\end_inset + +, so +\begin_inset Formula $P_{n}^{m}(\cos\theta)$ +\end_inset + + goes like +\begin_inset Formula $o(\theta^{2}),o\left((\theta-\pi)^{2}\right)$ +\end_inset + + at +\begin_inset Formula $0,\pi$ +\end_inset + +, which safely eliminates the divergent factor. + However, for +\begin_inset Formula $\left|m\right|=1$ +\end_inset + +, the whole expression +\begin_inset Formula $P_{n}^{m}(\cos\theta)/\sin\theta$ +\end_inset + + has a finite nonzero limit for +\begin_inset Formula $\theta\to0,\pi$ +\end_inset + +. + According to Mathematica (for +\begin_inset Formula $\theta\to\pi,$ +\end_inset + + Mathematica does not work well, but it can be derived from the +\begin_inset Formula $\theta\to0$ +\end_inset + + case and oddness/evenness). + +\begin_inset Formula +\begin{eqnarray*} +\lim_{\theta\to0}\frac{P_{n}^{1}(\cos\theta)}{\sin\theta} & = & -\frac{1}{2}n(1+n),\qquad\lim_{\theta\to0}\frac{P_{n}^{-1}(\cos\theta)}{\sin\theta}=\frac{1}{2},\\ +\lim_{\theta\to\pi}\frac{P_{n}^{1}(\cos\theta)}{\sin\theta} & = & \frac{\left(-1\right)^{n}}{2}n(1+n),\qquad\lim_{\theta\to\pi}\frac{P_{n}^{-1}(\cos\theta)}{\sin\theta}=\frac{\left(-1\right)^{n+1}}{2}. +\end{eqnarray*} + +\end_inset + +NOT COMPLETELY SURE ABOUT THE SIGN/NORMALIZATION CONVENTION HERE. + IT HAS TO BE CHECKED. +\end_layout + \begin_layout Standard Expansions for the scattered fields are \begin_inset CommandInset citation