A Hessian criterion for totally positive Toeplitz matrices and a new proof of Cattani's theorem in two variables

Cattani's theorem for graded Artinian Gorenstein algebras states that the ordinary Hodge-Riemann relations imply the mixed Hodge-Riemann relations under certain conditions. We give a new proof of this result for codimension two algebras. Our proof leads to a Hessian criterion for totally positive Toeplitz matrices, which is analogous to the Wronskian criterion for totally positive flags discovered recently by S. Karp.