Admissible interventions

For a joint output $B$, its actual influence set consists of input factors $a$ for which ${\mathrm{Sig}}_{\Phi }(\{a\}\to B)>0$. Equivalently, it is the union of tensor factors occurring in the minimal support of ${\Phi }_B^{\ast }(L({\mathcal{H}}_B))$. The equivalence follows from Theorem thm:nosignal and