Half-plane-capacity composition rule (source code)

= Half-plane-capacity composition rule

If compact H-hulls satisfy $A\subseteq C$ and $D$ is the bounded filling of $g_A(C\setminus A)$, then
$$
g_C=g_D\circ g_A,
\qquad
\operatorname{hcap}(C)
=\operatorname{hcap}(A)+\operatorname{hcap}(D).
$$
In particular, inclusion is strict exactly when the capacity increase is positive.