  Given a permutation P in Sn, let G(P) be the graph on n vertices {1,...,n},
where two vertices i<j are adjacent if i appears right of j in P and there are
no integers k with i<k<j and k appearing between i and j in P. Let G'(P) be the
graph obtained by dropping the condition that i appears right of j, i.e. two
vertices are adjacent if the rectangle [i,P(i)] x [j,P(j)] is empty. In the
study of the strong order on permutation, Adin and Roichman introduced these
graphs and computed their maximum number of edges. We generalize these results
to the Weyl group of signed permutations Bn, working with graphs on vertices
{-n,...,n}\{0}, using new variants of a classical theorem of Turan.
