Spectrahedrality of hyperbolicity cones of multivariate matching polynomials

The generalized Lax conjecture asserts that each hyperbolicity cone is a linear slice of the cone of positive semidefinite matrices. We prove the conjecture for a multivariate generalization of the matching polynomial. This is further extended (albeit in a weaker sense) to a multivariate version of the independence polynomial for simplicial graphs. As an application, we give a new proof of the conjecture for elementary symmetric polynomials (originally due to Brändén). Finally, we consider a hyperbolic convolution of determinant polynomials generalizing an identity of Godsil and Gutman.