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The cut sets of a graph are special sets of vertices whose removal disconnects the graph. They are fundamental in the study of binomial edge ideals, since they encode their minimal primary decomposition. We introduce the class of accessible…

Commutative Algebra · Mathematics 2022-01-04 Davide Bolognini , Antonio Macchia , Francesco Strazzanti

A combinatorial property that characterizes Cohen-Macaulay binomial edge ideals has long been elusive. A recent conjecture ties the Cohen-Macaulayness of a binomial edge ideal $J_G$ to special disconnecting sets of vertices of its…

Commutative Algebra · Mathematics 2022-12-20 Davide Bolognini , Antonio Macchia , Giancarlo Rinaldo , Francesco Strazzanti

We classify the bipartite graphs $G$ whose binomial edge ideal $J_G$ is Cohen-Macaulay. The connected components of such graphs can be obtained by gluing a finite number of basic blocks with two operations. In this context we prove the…

Commutative Algebra · Mathematics 2017-05-09 Davide Bolognini , Antonio Macchia , Francesco Strazzanti

We describe the simplicial complex $\Delta$ such that the initial ideal of $J_G$ is the Stanley-Reisner ideal of $\Delta$. By $\Delta$ we show that if $J_G$ is $(S_2)$ then $G$ is accessible. We also characterize all accessible blocks with…

Commutative Algebra · Mathematics 2021-08-03 Alberto Lerda , Carla Mascia , Giancarlo Rinaldo , Francesco Romeo

We study unmixed and Cohen-Macaulay properties of the binomial edge ideal of some classes of graphs. We compute the depth of the binomial edge ideal of a generalized block graph. We also characterize all generalized block graphs whose…

Commutative Algebra · Mathematics 2015-06-04 Dariush Kiani , Sara Saeedi Madani

Some recent investigations indicate that for the classification of Cohen-Macaulay binomial edge ideals, it suffices to consider biconnected graphs with some whiskers attached (in short, `block with whiskers'). This paper provides explicit…

Commutative Algebra · Mathematics 2024-09-04 Om Prakash Bhardwaj , Kamalesh Saha

Conca and Varbaro (Invent. Math. 221 (2020), no. 3) showed the equality of depth of a graded ideal and its initial ideal in a polynomial ring when the initial ideal is square-free. In this paper, we give some beautiful applications of this…

Commutative Algebra · Mathematics 2024-09-11 Kamalesh Saha , Indranath Sengupta

Let $G$ be a Cameron--Walker graph on $n$ vertices and $J_G$ the binomial edge ideal of $G$. Let $S$ denote the polynomial ring in $2n$ variables over a field. It is shown that the following conditions are equivalent: (i) $S/J_G$ is…

Commutative Algebra · Mathematics 2025-09-03 Takayuki Hibi , Sara Saeedi Madani

We relate homological properties of a binomial edge ideal $\mathcal{J}_G$ to invariants that measure the connectivity of a simple graph $G$. Specifically, we show if $R/\mathcal{J}_G$ is a Cohen-Macaulay ring, then graph toughness of $G$ is…

Commutative Algebra · Mathematics 2016-05-03 Arindam Banerjee , Luis Núñez-Betancourt

Let $G$ be a simple graph on $n$ vertices and let $J_{G,m}$ be the generalized binomial edge ideal associated to $G$ in the polynomial ring $K[x_{ij}, 1\le i \le m, 1\le j \le n]$. We classify the Cohen-Macaulay generalized binomial edge…

Commutative Algebra · Mathematics 2023-07-04 Luca Amata , Marilena Crupi , Giancarlo Rinaldo

We study weighted graphs and their "edge ideals" which are ideals in polynomial rings that are defined in terms of the graphs. We provide combinatorial descriptions of m-irreducible decompositions for the edge ideal of a weighted graph in…

Commutative Algebra · Mathematics 2013-02-26 Chelsey Paulsen , Sean Sather-Wagstaff

In this paper we provide a full combinatorial characterization of sequentially Cohen-Macaulay binomial edge ideals of closed graphs. In addition, we show that a binomial edge ideal of a closed graph is approximately Cohen-Macaulay if and…

Commutative Algebra · Mathematics 2022-07-12 Viviana Ene , Giancarlo Rinaldo , Naoki Terai

We characterize unmixed and Cohen-Macaulay edge-weighted edge ideals of very well-covered graphs. We also provide examples of oriented graphs which have unmixed and non-Cohen-Macaulay vertex-weighted edge ideals, while the edge ideal of…

Commutative Algebra · Mathematics 2020-03-30 Seyed Amin Seyed Fakhari , Kosuke Shibata , Naoki Terai , Siamak Yassemi

We first characterise graphs with binomial edge ideals of K\"onig type as those for which the path covering number is equal to a minor variant of the scattering number. These are well-studied graph-theoretic invariants, allowing us to apply…

Commutative Algebra · Mathematics 2026-05-26 David Williams

We prove that wheels and block graphs have sequentially Cohen-Macaulay binomial edge ideals. Moreover, we provide a construction of new families of sequentially Cohen-Macaulay graphs by cones.

Commutative Algebra · Mathematics 2025-07-08 Ernesto Lax , Giancarlo Rinaldo , Francesco Romeo

Several algebraic properties of a binomial edge ideal $J_G$ can be interpreted in terms of combinatorial properties of its associated graph $G$. In particular, the so-called cut sets of a graph $G$, special sets of vertices that disconnect…

Combinatorics · Mathematics 2025-01-30 Davide Bolognini , Antonio Macchia , Giancarlo Rinaldo , Francesco Strazzanti

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

Let $G=(V,E)$ be a graph. If $G$ is a K\"onig graph or $G$ is a graph without 3-cycles and 5-cycle, we prove that the following conditions are equivalent: $\Delta_{G}$ is pure shellable, $R/I_{\Delta}$ is Cohen-Macaulay, $G$ is unmixed…

Combinatorics · Mathematics 2015-05-04 Iván Dario Castrillón , Roberto Cruz , Enrique Reyes

Let $D$ be a weighted oriented graph, whose underlying graph is $G$, and let $I(D)$ be its edge ideal. If $G$ has no $3$-, $5$-, or $7$-cycles, or $G$ is K\"{o}nig, we characterize when $I(D)$ is unmixed. If $G$ has no $3$- or $5$-cycles,…

Commutative Algebra · Mathematics 2019-10-01 Yuriko Pitones , Enrique Reyes , Rafael H. Villarreal

Let $G$ be a simple graph on $n$ vertices and $J_G$ denote the binomial edge ideal of $G$ in the polynomial ring $S = \mathbb{K}[x_1, \ldots, x_n, y_1, \ldots, y_n].$ In this article, we compute the second graded Betti numbers of $J_G$, and…

Commutative Algebra · Mathematics 2020-10-22 A. V. Jayanthan , Arvind Kumar , Rajib Sarkar
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