TheIs the Laplacian operator $\Delta: C^2([a,b],\mathbb{R}) \to L^2(a,b)$ is unbounded. Could anyone give an illustrative example? Here $a,b \in\mathbb{R}$, $C^2([a,b],\mathbb{R})$ associated with $L^2$ norm.
HowIf yes, how can we "modify" these spaces to obtain a bounded operator?