23 research outputs found
The multivariate arithmetic Tutte polynomial
We introduce an arithmetic version of the multivariate Tutte polynomial recently studied by Sokal, and a quasi-polynomial that interpolates between the two. We provide a generalized Fortuin-Kasteleyn representation for representable arithmetic matroids, with applications to arithmetic colorings and flows. We give a new proof of the positivity of the coefficients of the arithmetic Tutte polynomial in the more general framework of pseudo-arithmetic matroids. In the case of a representable arithmetic matroid, we provide a geometric interpretation of the coefficients of the arithmetic Tutte polynomial. \ua9 2012 Discrete Mathematics and Theoretical Computer Science (DMTCS), Nancy, France
Zonotopes, toric arrangements, and generalized Tutte polynomials
We introduce a multiplicity Tutte polynomial M(x, y), which generalizes the ordinary one and has applications to zonotopes and toric arrangements. We prove that M(x, y) satisfies a deletion-restriction recurrence and has positive coefficients. The characteristic polynomial and the Poincar\ue9 polynomial of a toric arrangement are shown to be specializations of the associated polynomial M(x, y), likewise the corresponding polynomials for a hyperplane arrangement are specializations of the ordinary Tutte polynomial. Furthermore, M(1, y) is the Hilbert series of the related discrete Dahmen-Micchelli space, while M(x, 1) computes the volume and the number of integral points of the associated zonotope. \ua9 2010 Discrete Mathematics and Theoretical Computer Science (DMTCS), Nancy, France
Arithmetic matroids and Tutte polynomials
We introduce the notion of arithmetic matroid, whose main example is provided by a list of elements in a finitely generated abelian group. We study the representability of its dual, and, guided by the geometry of toric arrangements, we give a combinatorial interpretation of the associated arithmetic Tutte polynomial, which can be seen as a generalization of Crapo's formula
On the cohomology of arrangements of subtori
Given an arrangement of subtori of arbitrary codimension in a complex torus, we compute the cohomology groups of the complement. Then, by using the Leray spectral sequence, we describe the multiplicative structure on the associated graded cohomology. We also provide a differential model for the cohomology ring, by considering a toric wonderful model and its Morgan algebra. Finally, we focus on the divisorial case, proving a new presentation for the cohomology of toric arrangements
Universal Tutte characters via combinatorial coalgebras
The Tutte polynomial is the most general invariant of matroids and graphs
that can be computed recursively by deleting and contracting edges. We
generalize this invariant to any class of combinatorial objects with deletion
and contraction operations, associating to each such class a universal Tutte
character by a functorial procedure. We show that these invariants satisfy a
universal property and convolution formulae similar to the Tutte polynomial.
With this machinery we recover classical invariants for delta-matroids, matroid
perspectives, relative and colored matroids, generalized permutohedra, and
arithmetic matroids, and produce some new convolution formulae. Our principal
tools are combinatorial coalgebras and their convolution algebras. Our results
generalize in an intrinsic way the recent results of
Krajewski--Moffatt--Tanasa.Comment: Accepted version, 51p
Matroids over a ring
We introduce the notion of a matroid M over a commutative ring R, assigning to every subset of the ground set an R-module according to some axioms. When R is a field, we recover matroids. When R D Z, and when R is a DVR, we get (structures which contain all the data of) quasi-arithmetic matroids, and valuated matroids, i.e. tropical linear spaces, respectively. More generally, whenever R is a Dedekind domain, we extend all the usual properties and operations holding for matroids (e.g., duality), and we explicitly describe the structure of the matroids over R. Furthermore, we compute the Tutte-Grothendieck ring of matroids over R. We also show that the Tutte quasi-polynomial of a matroid over Z can be obtained as an evaluation of the class of the matroid in the Tutte-Grothendieck ring
On a Generalization of Zaslavsky's Theorem for Hyperplane Arrangements
We define arrangements of codimension-1 submanifolds in a smooth manifold
which generalize arrangements of hyperplanes. When these submanifolds are
removed the manifold breaks up into regions, each of which is homeomorphic to
an open disc. The aim of this paper is to derive formulas that count the number
of regions formed by such an arrangement. We achieve this aim by generalizing
Zaslavsky's theorem to this setting. We show that this number is determined by
the combinatorics of the intersections of these submanifolds.Comment: version 3: The title had a typo in v2 which is now fixed. Will appear
in Annals of Combinatorics. Version. 2: 19 pages, major revision in terms of
style and language, some results improved, contact information updated, final
versio
THE MULTIVARIATE ARITHMETIC TUTTE POLYNOMIAL
We introduce an arithmetic version of the multivariate Tutte polynomial and a quasi-polynomial that interpolates between the two. A generalized Fortuin-Kasteleyn representation with applications to arithmetic colorings and flows is obtained. We give a new and more general proof of the positivity of the coefficients of the arithmetic Tutte polynomial and (in the representable case) a geometrical interpretation of them
A TUTTE POLYNOMIAL FOR TORIC ARRANGEMENTS
We introduce a multiplicity Tutte polynomial M(x,y), with applications to zonotopes and toric arrangements. We prove that M(x,y) satisfies a deletion-restriction recurrence and has positive coefficients. The characteristic polynomial and the Poincare' polynomial of a toric arrangement are shown to be specializations of the associated polynomial M(x,y), likewise the corresponding polynomials for a hyperplane arrangement are specializations of the ordinary Tutte polynomial. Furthermore, M(1,y) is the Hilbert series of the related discrete Dahmen-Micchelli space, while M(x,1) computes the volume and the number of integral points of the associated zonotope
Polyhedra and parameter spaces for matroids over valuation rings
In this paper we address two of the major foundational questions in the theory of matroids over rings. First, we provide a cryptomorphic axiomatisation, by introducing an analogue of the base polytope for matroids. Second, we describe a parameter space for matroids over a valuation ring, which turns out to be a tropical version of the Bott-Samelson varieties for the full flag variety. Thus a matroid over a valuation ring is a sequence of flags of tropical linear spaces a.k.a. valuated matroids