# Riesz measure of a smooth subharmonic function on a ball

Let $$B(x_{0},r)$$ be the ball of center $$x_{0}$$ and radius $$r>0$$ in $$\mathbb{R}^{k}$$ ($$k\geq2$$), and $$u$$ a subharmonic function on an open neighborhood of the closure of $$B(x_{0},r)$$. Let $$\mu$$ be the Riesz measure of $$u$$ on this ball. If $$u$$ is $$C^{2}-$$smooth, is it true that $$\mu=\Delta u$$, the laplacian of $$u$$? Do you know a reference for that?

• Except a constant multiple which depends on the dimension. Oct 31 '18 at 13:33