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We consider three classes of random graphs: edge random graphs, vertex random graphs, and vertex-edge random graphs. Edge random graphs are Erdos-Renyi random graphs, vertex random graphs are generalizations of geometric random graphs, and…

Combinatorics · Mathematics 2010-10-14 Elizabeth Beer , James Allen Fill , Svante Janson , Edward R. Scheinerman

A graph $G$ is $\textit{universal}$ for a (finite) family $\mathcal{H}$ of graphs if every $H \in \mathcal{H}$ is a subgraph of $G$. For a given family $\mathcal{H}$, the goal is to determine the smallest number of edges an…

Combinatorics · Mathematics 2024-01-12 Noga Alon , Natalie Dodson , Carmen Jackson , Rose McCarty , Rajko Nenadov , Lani Southern

In this paper, we study the componentwise linearity of edge ideals of weighted oriented graphs. We show that if $D$ is a weighted oriented graph whose edge ideal $I(D)$ is componentwise linear, then the underlying simple graph $G$ of $D$ is…

Commutative Algebra · Mathematics 2023-10-02 Manohar Kumar , Ramakrishna Nanduri , Kamalesh Saha

Let I=I(D) be the edge ideal of a weighted oriented graph D. We determine the irredundant irreducible decomposition of I. Also, we characterize the associated primes and the unmixed property of I. Furthermore, we give a combinatorial…

Commutative Algebra · Mathematics 2020-12-08 Yuriko Pitones , Enrique Reyes , Jonathan Toledo

In this paper we prove the conjectured upper bound for Castelnuovo-Mumford regularity of binomial edge ideals posed in [23], in the case of chordal graphs. Indeed, we show that the regularity of any chordal graph G is bounded above by the…

Commutative Algebra · Mathematics 2018-10-09 M. Rouzbahani Malayeri , S. Saeedi Madani , D. Kiani

We consider Stanley--Reisner rings $k[x_1,...,x_n]/I(\mc{H})$ where $I(\mc{H})$ is the edge ideal associated to some particular classes of hypergraphs. For instance, we consider hypergraphs that are natural generalizations of graphs that…

Commutative Algebra · Mathematics 2015-10-12 Eric Emtander , Fatemeh Mohammadi , Somayeh Moradi

A connected and nonempty graph A is defined as generalized t-edge distance-balanced, while for each edge f={\alpha}\{beta} the number of edges nearer to {\alpha} than \{beta} are equal to t-times of edges nearer to \{beta} than to {\alpha},…

Combinatorics · Mathematics 2023-12-25 Zohreh Aliannejadi , Mehdi Alaeiyan , Alireza Gilani

We determine (multi)graded Betti numbers of path ideals of lines and star graphs.

Commutative Algebra · Mathematics 2014-10-31 Nursel Erey

We associate a sequence of positive integers, termed the type sequence, with a cochordal graph. Using this type sequence, we compute all graded Betti numbers of its edge ideal. We then classify all positive integer $n$ such that the zero…

Commutative Algebra · Mathematics 2024-11-13 Le Xuan Dung , Thanh Vu

In this article we obtain an improved upper bound for the regularity of binomial edge ideals of trees.

Commutative Algebra · Mathematics 2018-08-21 A. V. Jayanthan , N. Narayanan , B. V. Raghavendra Rao

The well-known 1-2-3 Conjecture asserts that the edges of every graph without isolated edges can be weighted with $1$, $2$ and $3$ so that adjacent vertices receive distinct weighted degrees. This is open in general, while it is known to be…

Combinatorics · Mathematics 2019-12-19 Jakub Przybyło

For the edge ideal I of an arbitrary simple graph G we describe the monomials of the saturation of a power of I in terms of (vertex) weighted graphs associated with the monomials. This description allows us to characterize the embedded…

Commutative Algebra · Mathematics 2014-12-01 Ha Thi Thu Hien , Ha Minh Lam , Ngo Viet Trung

We prove two recent conjectures on some upper bounds for the Castelnuovo-Mumford regularity of the binomial edge ideals of some different classes of graphs. We prove the conjecture of Matsuda and Murai for graphs which has a cut edge or a…

Commutative Algebra · Mathematics 2013-11-19 Dariush Kiani , Sara Saeedi Madani

We prove several cases of the Betti number conjecture for the binomial edge ideal $J_G$ of a proper interval graph $G$ (also known as closed graph). Namely, we show that this conjecture is true for the linear strand of $J_G$, and true in…

Commutative Algebra · Mathematics 2016-12-01 Herolistra Baskoroputro

Let $G$ be a simple graph on $n$ vertices and $J_G$ denote the corresponding binomial edge ideal in $S = K[x_1, \ldots, x_n, y_1,\ldots, y_n].$ We prove that the Castelnuovo-Mumford regularity of $J_G$ is bounded above by $c(G)+1$ when $G$…

Combinatorics · Mathematics 2021-08-20 Arvind Kumar

We characterize the graphs $G$ for which their toric ideals $I_G$ are complete intersections. In particular we prove that for a connected graph $G$ such that $I_G$ is complete intersection all of its blocks are bipartite except of at most…

Commutative Algebra · Mathematics 2011-10-06 Christos Tatakis , Apostolos Thoma

We investigate, using the notion of linear quotients, significative classes of connected graphs whose monomial edge ideals, not necessarily squarefree, have linear resolution, in order to compute standard algebraic invariants of the…

Rings and Algebras · Mathematics 2012-10-30 Maurizio Imbesi , Monica La Barbiera

Let $G$ be a graph and let $I = I(G)$ be its edge ideal. When $G$ is unicyclic, we give a decomposition of symbolic powers of $I$ in terms of its ordinary powers. This allows us to explicitly compute the Waldschmidt constant and the…

Commutative Algebra · Mathematics 2019-02-26 Yan Gu , Huy Tai Ha , Jonathan L. O'Rourke , Joseph W. Skelton

This article provides structural characterization of simple graphs whose edge-set can be partitioned into maximum matchings. We use Vizing's classification of simple graphs based on edge chromatic index.

Combinatorics · Mathematics 2012-10-19 Niraj Khare

In this note we prove that every closed graph $G$ is up to isomorphism a proper interval graph. As a consequence we obtain that there exist linear-time algorithms for closed graph recognition.

Combinatorics · Mathematics 2012-11-27 Marilena Crupi , Giancarlo Rinaldo