Sommerfeld Radiation Condition

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This is a condition for the Frequency Domain Problem that the scattered wave is only outgoing at infinity. It depends on the convention regarding whether the time dependence is \exp (i\omega t)\, or \exp (-i\omega t)\, Assuming the former (which is the standard convention on this wiki) In two-dimensions the condition is


\sqrt{|{x}|}\left(  \frac{\partial}{\partial|x|}+{i}k\right)
(\phi-\phi^{\mathrm{{In}}})=0,\;\mathrm{{as\;}}|x|\rightarrow\infty\mathrm{.}

where φIn is the incident potential and k is the wave number.

In three-dimensions the condition is


|\mathbf{r}|\left(  \frac{\partial}{\partial|\mathbf{r}|}+{i}k\right)
(\phi-\phi^{\mathrm{{In}}})=0,\;\mathrm{{as\;}}|\mathbf{r}|\rightarrow\infty\mathrm{.}

If the time dependence is assumed to be \exp (-i\omega t)\, then we have in two-dimensions


\sqrt{|{x}|} \left(  \frac{\partial}{\partial|x|}-{i}k\right)
(\phi-\phi^{\mathrm{{In}}})=0,\;\mathrm{{as\;}}|x|\rightarrow\infty\mathrm{.}

and in three-dimensions


|\mathbf{r}|\left(  \frac{\partial}{\partial|\mathbf{r}|}-{i}k\right)
(\phi-\phi^{\mathrm{{In}}})=0,\;\mathrm{{as\;}}|\mathbf{r}|\rightarrow\infty\mathrm{.}

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