Lefschetz properties of monomial ideals and mixed multiplicities
Given a polynomial ring S over a field of characteristic zero and an Artinian ring A=S/I where I is a monomial ideal, we build a new polynomial ring SI with the variables being the nonzero monomials of A. For every degree i, we define two ideals in SI such that their analytic spread detects the WLP property of A in degree i:
1. The jacobian ideal of a hyperplane arrangement, when I is any monomial ideal
2. The edge ideal of a hypergraph, when all the nonzero monomials of A are squarefree.
In particular, when all the nonzero monomials of A are squarefree, we see the connections between birational maps and the failure of WLP in positive characteristics.