I came across the expression
$$\Vert\nabla f\Vert_{L^2(\Omega)}$$
for some function $f: \Omega \subset \mathbb R^2 \to \mathbb R$, but I couldn't find the definition. Can anyone tell me how the $L^2$ norm of a gradient is defined?
My best guess is
$$\sqrt{ \int_\Omega |\nabla f|^2 dx}$$
where $|\nabla f|^2 = (\partial_{x_1} f)^2 + (\partial_{x_2} f)^2$, but I'm not sure whether this is correct.