Lee-Yang Problems and The Geometry of Multivariate Polynomials
  We describe all linear operators on spaces of multivariate polynomials preserving the property of being non-vanishing in open circular domains. This completes the multivariate generalization of the classification program initiated by P\'olya-Schur for univariate real polynomials and provides a natural framework for dealing in a uniform way with Lee-Yang type problems in statistical mechanics, combinatorics, and geometric function theory.   This is an announcement with some of the main results in arXiv:0809.0401 and arXiv:0809.3087. 
Julius Borcea, Petter Br\"and\'en