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A famous theorem of Kalai and Meshulam is that $\mathrm{reg}(I + J) \leq \mathrm{reg}(I) + \mathrm{reg}(J) -1$ for any squarefree monomial ideals $I$ and $J$. This result was subsequently extended by Herzog to the case where $I$ and $J$ are…

Commutative Algebra · Mathematics 2024-05-24 Adam LaClair

Let G be a graph obtained by taking r>=2 paths and identifying all first vertices and identifying all the last vertices. We compute the Castelnuovo--Mumford regularity of the quotient S/I(X), where S is the polynomial ring on the edges of G…

Commutative Algebra · Mathematics 2016-06-29 Antonio Macchia , Jorge Neves , Maria Vaz Pinto , Rafael H. Villarreal

Let $X$ be the Hankel matrix of size $2\times n$ and let $G$ be a closed graph on the vertex set $[n].$ We study the binomial ideal $I_G\subset K[x_1,\ldots,x_{n+1}]$ which is generated by all the $2$-minors of $X$ which correspond to the…

Commutative Algebra · Mathematics 2014-06-17 Faryal Chaudhry , Ahmet Dokuyucu , Viviana Ene

We prove that the projective dimension of any (hyper)graph can be bounded from above by the (Castelnuovo-Mumford) regularity of its Levi graph (or incidence bipartite graph). This in particular brings the use of regularity's upper bounds on…

Combinatorics · Mathematics 2016-05-11 Türker Bıyıkoğlu , Yusuf Civan

We obtain an improved lower bound for the regularity of the binomial edge ideals of trees. We prove an upper bound for the regularity of the binomial edge ideals of certain subclass of block-graphs. As a consequence we obtain sharp upper…

Commutative Algebra · Mathematics 2018-04-30 A. V. Jayanthan , N. Narayanan , B. V. Raghavendra Rao

Let $G$ be a finite simple graph and $I(G)$ denote the corresponding edge ideal. For all $s \geq 1$, we obtain upper bounds for reg$(I(G)^s)$ for bipartite graphs. We then compare the properties of $G$ and $G'$, where $G'$ is the graph…

Commutative Algebra · Mathematics 2016-09-07 A V Jayanthan , N Narayanan , S Selvaraja

We provide a characterisation of all graphs whose parity binomial edge ideals have pure resolutions. In particular, we show that the minimal free resolution of a parity binomial edge ideal is pure if and only if the corresponding graph is a…

Commutative Algebra · Mathematics 2020-11-17 Peter Phelan

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

A graph $G$ is well-covered if it has no isolated vertices and all the maximal independent sets have the same cardinality. If furthermore two times this cardinality is equal to $|V(G)|$, the graph $G$ is called very well-covered. The class…

Commutative Algebra · Mathematics 2010-06-08 Mohammad Mahmoudi , Amir Mousivand , Marilena Crupi , Giancarlo Rinaldo , Naoki Terai , Siamak Yassemi

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

In this study, we investigate the binomial edge ring associated with the skew Ferrers diagram. By employing Sagbi basis theory, we construct a quadratic Gr\"{o}bner basis for its defining ideal. As an application, we prove that this ring is…

Commutative Algebra · Mathematics 2025-08-29 Kuei-Nuan Lin , Yi-Huang Shen

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 introduce a family of graphs, which we call down-left graphs, and study their combinatorial and algebraic properties. We show that members of this family are well-covered, $C_5$-free, and vertex decomposable. By applying a result of…

Commutative Algebra · Mathematics 2025-04-30 Jennifer Biermann , Beth Anne Castellano , Marcella Manivel , Eden Petrucelli , Adam Van Tuyl

We classify all unicycle graphs whose edge-binomials form a $d$-sequence, particularly linear type binomial edge ideals. We also classify unicycle graphs whose parity edge-binomials form a $d$-sequence. We study the regularity of powers of…

Commutative Algebra · Mathematics 2024-03-19 Marie Amalore Nambi , Neeraj Kumar

In this paper we consider bi-Cohen-Macaulay graphs, and give a complete classification of such graphs in the case they are bipartite or chordal. General bi-Cohen-Macaulay graphs are classified up to separation. The inseparable…

Commutative Algebra · Mathematics 2015-08-31 Jürgen Herzog , Ahad Rahimi

We prove the multiplicity bounds conjectured by Herzog-Huneke-Srinivasan and Herzog-Srinivasan in the following cases: the strong conjecture for edge ideals of bipartite graphs, and the weaker Taylor bound conjecture for all quadratic…

Commutative Algebra · Mathematics 2007-10-16 Manoj Kummini

We give a bound on the Castelnuovo-Mumford regularity of a homogeneous ideals I, in a polynomial ring A, in terms of number of variables and the degrees of generators, when the dimension of A/I is at most two. This bound improves the one…

Commutative Algebra · Mathematics 2007-05-23 Marc Chardin , Amadou Lamine Fall

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

Edge ideals of finite simple graphs are well-studied over polynomial rings. In this paper, we initiate the study of edge ideals over exterior algebras, specifically focusing on the depth and singular varieties of such ideals. We prove an…

Commutative Algebra · Mathematics 2022-08-09 Matthew Mastroeni , Jason McCullough , Andrew Osborne , Joshua Rice , Cole Willis

In this paper, we first give some sufficient criteria for normality of monomial ideals. As applications, we show that closed neighborhood ideals of complete bipartite graphs are normal, and hence satisfy the (strong) persistence property.…

Commutative Algebra · Mathematics 2023-08-15 Mehrdad Nasernejad , Somayeh Bandari , Leslie G. Roberts