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We study Brill-Noether existence on a finite graph using methods from polyhedral geometry and lattices. We start by formulating analogues of the Brill-Noether conjectures (both the existence and non-existence parts) for…

Combinatorics · Mathematics 2022-03-01 Madhusudan Manjunath

We define a free product of connected simple graphs that is equivalent to several existing definitions when the graphs are vertex-transitive but differs otherwise. The new definition is designed for the automorphism group of the free…

Group Theory · Mathematics 2021-09-30 Max Carter , Stephan Tornier , George A. Willis

In this paper, we continue the program initiated by I. Beck's now classical paper concerning zero-divisor graphs of commutative rings. After the success of much research regarding zero-divisor graphs, many authors have turned their…

Commutative Algebra · Mathematics 2014-01-03 Christopher Park Mooney

We study the problem of computing the rank of a divisor on a finite graph, a quantity that arises in the Riemann-Roch theory on a finite graph developed by Baker and Norine (Advances of Mathematics, 215(2): 766-788, 2007). Our work consists…

Combinatorics · Mathematics 2011-12-01 Madhusudan Manjunath

We study special linear systems called "very special" whose dimension does not satisfy a Clifford type inequality given by Huisman. We classify all these very special linear systems when they are compounded of an involution. Examples of…

Algebraic Geometry · Mathematics 2014-02-26 Jean-Philippe Monnier

We consider fair allocation of indivisible items under an additional constraint: there is an undirected graph describing the relationship between the items, and each agent's share must form a connected subgraph of this graph. This framework…

Computer Science and Game Theory · Computer Science 2017-06-07 Sylvain Bouveret , Katarína Cechlárová , Edith Elkind , Ayumi Igarashi , Dominik Peters

We introduce the notion of semibreak divisors on metric graphs (tropical curves) and prove that every effective divisor class (of degree at most the genus) has a semibreak divisor representative. This appropriately generalizes the notion of…

Algebraic Geometry · Mathematics 2018-07-04 Andreas Gross , Farbod Shokrieh , Lilla Tóthmérész

Given a real curve, we study special linear systems called "very special" for which the dimension does not satisfy a Clifford type inequality. We classify all these very special linear systems when the gonality of the curve is small.

Algebraic Geometry · Mathematics 2013-04-08 Jean-Philippe Monnier

Linear-width is a well-known and highly regarded graph parameter. The concept of Single Ideal and Linear obstacle serves as an obstruction to linear-width on a connectivity sysem. In this concise paper, we present an alternative proof for…

Discrete Mathematics · Computer Science 2026-03-03 Takaaki Fujita

Inspired by a very recent work of A. {\DH}uri\'c, S. Jev{\dj}eni\'c and N. Stopar, we introduce a new definition of zero-divisor graphs attached to rings, that includes all of the classical definitions already known in the literature. We…

Commutative Algebra · Mathematics 2022-03-08 Enrico Sbarra , Maurizio Zanardo

This article investigates the properties of order-divisor graphs associated with finite groups. An order-divisor graph of a finite group is an undirected graph in which the set of vertices includes all elements of the group, and two…

Group Theory · Mathematics 2024-08-30 Shafiq ur Rehman , Raheela Tahir , Farhat Noor

In this paper, we introduce a family of graphs which is a generalization of zero-divisor graphs and compute an upper-bound for the diameter of such graphs. We also investigate their cycles and cores.

Rings and Algebras · Mathematics 2020-08-19 Peyman Nasehpour

The proper divisor graph $\Upsilon_n$ of a positive integer $n$ is the simple graph whose vertices are the proper divisors of $n$, and in which two distinct vertices $u, v$ are adjacent if and only if $n$ divides $uv$. The graph…

Combinatorics · Mathematics 2020-05-12 Hitesh Kumar , Kamal Lochan Patra , Binod Kumar Sahoo

A degeneration of a smooth projective curve to a strongly stable curve gives rise to a specialization map from divisors on curves to divisors on graphs. In this paper we show that this specialization behaves well under the presence of real…

Algebraic Geometry · Mathematics 2010-05-20 Marc Coppens

In this paper, we study commutative zero-divisor semigroups determined by graphs. We prove a uniqueness theorem for a class of graphs. We show two classes of graphs that have no corresponding semigroups. In particular, any complete graph…

Rings and Algebras · Mathematics 2007-05-23 Tongsuo Wu , Li Chen

Let $X$ be a semistable curve and $L$ a line bundle whose multidegree is uniform, i.e., in the range between those of the structure sheaf and the dualizing sheaf of $X$. We establish an upper bound for $h^0(X,L)$, which generalizes the…

Algebraic Geometry · Mathematics 2022-11-02 Karl Christ

We study the binomial and monomial ideals arising from linear equivalence of divisors on graphs from the point of view of Gr\"obner theory. We give an explicit description of a minimal Gr\"obner bases for each higher syzygy module. In each…

Combinatorics · Mathematics 2019-10-21 Fatemeh Mohammadi , Farbod Shokrieh

We study various binomial and monomial ideals arising in the theory of divisors, orientations, and matroids on graphs. We use ideas from potential theory on graphs and from the theory of Delaunay decompositions for lattices to describe…

Combinatorics · Mathematics 2015-11-24 Fatemeh Mohammadi , Farbod Shokrieh

We prove that the (divisorial) gonality of a finite connected graph is lower bounded by its treewidth. We show that equality holds for grid graphs and complete multipartite graphs. We prove that the treewidth lower bound also holds for…

Combinatorics · Mathematics 2022-01-04 Josse van Dobben de Bruyn , Dion Gijswijt

Metric graphs are ubiquitous in science and engineering. For example, many data are drawn from hidden spaces that are graph-like, such as the cosmic web. A metric graph offers one of the simplest yet still meaningful ways to represent the…

Computational Geometry · Computer Science 2017-12-05 Tamal K. Dey , Dayu Shi , Yusu Wang