Galois groups of multivariate Tutte polynomials

Abstract

The multivariate Tutte polynomial ${\hat{Z}}_M$ of a matroid $M$ is a generalization of the standard two-variable version, obtained by assigning a separate variable $v_e$ to each element $e$ of the ground set $E$. It encodes the full structure of $M$. Let $\bv = \{v_e\}_{e\in E}$, let $K$ be an arbitrary field, and suppose $M$ is connected. We show that ${\hat{Z}}_M$ is irreducible over $K(\bv)$, and give three self-contained proofs that the Galois group of ${\hat{Z}}_M$ over $K(\bv)$ is the symmetric group of degree $n$, where $n$ is the rank of $M$. An immediate consequence of this result is that the Galois group of the multivariate Tutte polynomial of any matroid is a direct product of symmetric groups. Finally, we conjecture a similar result for the standard Tutte polynomial of a connected matroid.

8 pages, final version, to appear in J. Alg. Comb. Substantial revisions, including the addition of two alternative proofs of the main result

References in corpus (1)

• The multivariate Tutte polynomial (alias Potts model) for graphs and matroids