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Math 6410 • ODE

Winter 2004 • Question 11

Distributions. Let \(k(x,y)=\frac {1}{2\pi }\log \lvert x-y\rvert \), where \(x,y\in \mathbb {R}^2\).

  1. Show that \(k(\cdot ,y)\) is a distribution on \(\mathbb {R}^2\) for each \(y\in \mathbb {R}^2\).
  2. Show that as distributions, \(\Delta _x k(x,y)=\delta _y(x)\) for all \(y\in \mathbb {R}^2\). [\(\delta _y(x)=\delta (x-y)\) and \(\delta \) is the Dirac delta function.]

Raw LaTeX

\textbf{Distributions.}
Let \(k(x,y)=\frac{1}{2\pi}\log\lvert x-y\rvert\), where \(x,y\in\R^2\).
\begin{enumerate}
\item[(a.)] Show that \(k(\cdot,y)\) is a distribution on \(\R^2\) for each \(y\in\R^2\).
\item[(b.)] Show that as distributions, \(\Delta_x k(x,y)=\delta_y(x)\) for all
\(y\in\R^2\). [\(\delta_y(x)=\delta(x-y)\) and \(\delta\) is the Dirac delta function.]
\end{enumerate}