Triangularity of the Jacobian on siphon faces, the Metzler property of its transversal component and other results

We establish two structural properties of the Jacobian of a positive ODE on any invariant boundary face, i.e. on the face defined by a siphon of an associated Chemical Reaction Network. First, the Jacobian is block lower-triangular at every point of such a face, with a transversal diagonal block, wh