Polynomials with the half-plane property and the support theorems

  • Authors:
  • YoungBin Choe

  • Affiliations:
  • Combinatorial and Computational Mathematics Center, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea

  • Venue:
  • Journal of Combinatorial Theory Series B
  • Year:
  • 2005

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Abstract

A polynomial P(x) in n complex variables is said to have the half-plane property if P(x) ≠ 0 whenever all the variables have positive real parts. The generating polynomial for the set of all spanning trees of a graph G is one example. Motivated by the fact that the edge set of each spanning tree of G is a basis of the graphic matroid induced by G, it is shown by Choe et al. (Adv. Appl. Math. 32 (2004) 88-187) that the support of any homogeneous multiaffine polynomial with the half-plane property constitutes the set of all bases of a matroid. In this paper we show, when all the terms of a polynomial with the half-plane property have degrees of same parity, the support constitutes a jump system which is a generalization of matroids. Open problems and a few directions for further research will also be discussed.