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A graph $G$ is $\alpha$-excellent if every vertex of $G$ is contained in some maximum independent set of $G$. In this paper, we characterize $\alpha$-excellent bipartite graphs, $\alpha$-excellent unicyclic graphs, $\alpha$-excellent…

Combinatorics · Mathematics 2022-08-19 M. Dettlaff , M. A. Henning , J. Topp

We determine all possible triples of depth, dimension, and regularity of edge ideals of weighted oriented graphs with a fixed number of vertices. Also, we compute all the possible Betti table sizes of edge ideals of weighted oriented trees…

Commutative Algebra · Mathematics 2025-04-18 Trung Chau , Richie Sheng , Deborah Wooton

We give a combinatorial characterisation of connected graphs whose binomial edge ideals are of K\"{o}nig type, developed independently to the similar characterisation given by LaClair in arXiv:2304.13299, and exhibit some classes of graphs…

Commutative Algebra · Mathematics 2024-12-16 David Williams

A graph $G$ is $k$-edge geodetic graph if every edge of $G$ lies in at least one geodesic of length $k$. We studied some basic properties of $k$-edge geodetic graphs. We investigated the $k$ edge-geodeticity of complete bipartite graph…

Combinatorics · Mathematics 2024-08-13 Satyam Guragain , Ravi Srivastava

Let $I(G)^{[k]}$ denote the $k^{th}$ square-free power of the edge ideal $I(G)$ of a graph $G$. In this article, we provide a precise formula for the depth of $I(G)^{[k]}$ when $G$ is a Cohen-Macaulay forest. Using this, we show that for a…

Commutative Algebra · Mathematics 2024-11-05 Kanoy Kumar Das , Amit Roy , Kamalesh Saha

A Cameron-Walker graph is a graph for which the matching number and the induced matching number are the same. Assume that $G$ is a Cameron-Walker graph with edge ideal $I(G)$, and let $\ind-match(G)$ be the induced matching number of $G$.…

Commutative Algebra · Mathematics 2019-07-08 S. A. Seyed Fakhari

A biclique of a graph $G$ is an induced complete bipartite subgraph of $G$ such that neither part is empty. A star is a biclique of $G$ such that one part has exactly one vertex. The star graph of $G$ is the intersection graph of the…

Let G be a finite simple graph and let indm(G) and ordm(G) denote the induced matching number and the ordered matching number of G, respectively. We characterize all bipartite graphs G with indm(G) = ordm(G). We establish the…

Commutative Algebra · Mathematics 2025-03-28 A. V. Jayanthan , S. A. Seyed Fakhari , I. Swanson , S. Yassemi

Let $G$ be a simple graph on the vertex set $V(G) = [n] = \{1,...,n\}$ and edge ideal $E(G)$. We consider the class of closed graphs. A closed graph is a simple graph satisfying the following property: for all edges $\{i, j\}$ and $\{k,…

Commutative Algebra · Mathematics 2011-09-28 Marilena Crupi , Giancarlo Rinaldo

Let $G$ be a finite simple graph on $n$ non-isolated vertices, and let $J_G$ be its binomial edge ideal. We determine almost all pairs $(\text{projdim}(J_G),\text{reg}(J_G))$, where $G$ ranges over all finite simple graphs on $n$…

Commutative Algebra · Mathematics 2025-01-15 Antonino Ficarra , Emanuele Sgroi

In this paper, we explicitly give combinatorial formulas for the regularity of powers of edge ideals, $\reg(I(D)^k)$, of weighted oriented unmixed forests $D$ whose leaves are sinks ($V^+(D)$ are sinks). This combinatorial formula is a…

Commutative Algebra · Mathematics 2022-09-07 Manohar Kumar , Ramakrishna Nanduri

Let $G$ be a simple connected graph with vertex set $V(G)$ and edge set $E(G)$. A $k$-matching of a graph $G$ is a function $f:E(G)\rightarrow \{0,1,\ldots, k\}$ satisfying $\sum_{e \in E_G(v)} f(e) \leq k$ for every vertex $v \in V(G)$,…

Combinatorics · Mathematics 2026-02-23 Kexin Yang , Ligong Wang , Zhenhao Zhang

It is shown that if the binomial edge ideal of a graph $G$ defines a Koszul algebra, then $G$ must be chordal and claw free. A converse of this statement is proved for a class of chordal and claw free graphs.

Commutative Algebra · Mathematics 2013-10-25 Viviana Ene , Jürgen Herzog , Takayuki Hibi

If $G$ is a bridgeless cubic graph, Fulkerson conjectured that we can find 6 perfect matchings $M_1,...,M_6$ of $G$ with the property that every edge of $G$ is contained in exactly two of them and Berge conjectured that its edge set can be…

Discrete Mathematics · Computer Science 2009-04-09 Jean-Luc Fouquet , Jean-Marie Vanherpe

Two-dimensional squarefree monomial ideals can be seen as the Stanley-Reisner ideals of graphs. The main results of this paper are combinatorial characterizations for the Cohen-Macaulayness of ordinary and symbolic powers of such an ideal…

Commutative Algebra · Mathematics 2010-03-11 Nguyen Cong Minh , Ngo Viet Trung

We characterize all graphs whose binomial edge ideals have pure resolutions. Moreover, we introduce a new switching of graphs which does not change some algebraic invariants of graphs, and using this, we study the linear strand of the…

Combinatorics · Mathematics 2014-01-22 Dariush Kiani , Sara Saeedi Madani

Let $H$ be a simple undirected graph. The family of all matchings of $H$ forms a simplicial complex called the matching complex of $H$. Here , we give a classification of all graphs with a Gorenstein matching complex. Also we study when the…

Commutative Algebra · Mathematics 2024-04-11 Ashkan Nikseresht

We show that for the edge ideals of the graphs consisting of one cycle or two cycles of any length connected through a vertex or a path, the arithmetical rank equals the projective dimension.

Commutative Algebra · Mathematics 2015-10-19 Margherita Barile , Dariush Kiani , Fatemeh Mohammadi , Siamak Yassemi

Let $J_G$ denote the binomial edge ideal of a connected undirected graph on $n$ vertices. This is the ideal generated by the binomials $x_iy_j - x_jy_i, 1\leq i < j \leq n,$ in the polynomial ring $S= K[x_1,...,x_n,y_1,...,y_n]$ where…

Commutative Algebra · Mathematics 2013-01-07 Peter Schenzel , Sohail Zafar

Let $\mathcal{D}$ be a weighted oriented graph and $I(\mathcal{D})$ be its edge ideal. In this paper, we show that all the symbolic and ordinary powers of $I(\mathcal{D})$ coincide when $\mathcal{D}$ is a weighted oriented certain class of…

Commutative Algebra · Mathematics 2021-06-01 Arindam Banerjee , Kanoy Kumar Das , S. Selvaraja