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Given a set D of nonnegative integers, we derive the asymptotic number of graphs with a givenvnumber of vertices, edges, and such that the degree of every vertex is in D. This generalizes existing results, such as the enumeration of graphs…

组合数学 · 数学 2015-07-22 Élie de Panafieu , Lander Ramos

We give an explicit formula for the Hilbert-Poincar\'{e} series of the parity binomial edge ideal of a complete graph $K_{n}$ or equivalently for the ideal generated by all $2\times 2$-permanents of a $2\times n$-matrix. It follows that the…

交换代数 · 数学 2020-03-03 Do Trong Hoang , Thomas Kahle

The purpose of this paper is to give a simple geometric construction of ideals whose Castelnuovo-Mumford regularity is large compared to the generating degree. Moreover, our ideals have the property that the Castelnuovo-Mumford regularity…

代数几何 · 数学 2014-03-11 Brooke Ullery

We prove an asymptotic formula for the number of $k$-uniform hypergraphs with a given degree sequence, for a wide range of parameters. In particular, we find a formula that is asymptotically equal to the number of $d$-regular $k$-uniform…

组合数学 · 数学 2022-02-01 Nina Kamčev , Anita Liebenau , Nick Wormald

A $3$-uniform hypergraph is a generalization of simple graphs where each hyperedge is a subset of vertices of size $3$. The degree of a vertex in a hypergraph is the number of hyperedges incident with it. The degree sequence of a hypergraph…

组合数学 · 数学 2023-12-04 Runze Li , Istvan Miklos

We find an asymptotic enumeration formula for the number of simple $r$-uniform hypergraphs with a given degree sequence, when the number of edges is sufficiently large. The formula is given in terms of the solution of a system of equations.…

组合数学 · 数学 2022-05-18 Catherine Greenhill , Mikhail Isaev , Tamás Makai , Brendan D. McKay

We give characterizations of the structure and degree sequences of hereditary unigraphs, those graphs for which every induced subgraph is the unique realization of its degree sequence. The class of hereditary unigraphs properly contains the…

组合数学 · 数学 2015-08-04 Michael D. Barrus

When $I$ is the edge ideal of a graph $G$, we use combinatorial properities, particularly Property $P$ on connectivity of neighbors of an edge, to classify when a binomial sum of vertices is a regular element on $R/I(G)$. Under a mild…

交换代数 · 数学 2024-12-16 Joseph Brennan , Susan Morey

An Eulerian orientation is an orientation of the edges of a graph such that every vertex is balanced: its in-degree equals its out-degree. Counting Eulerian orientations corresponds to the crucial partition function in so-called ``ice-type…

组合数学 · 数学 2024-12-23 Mikhail Isaev , Brendan D. McKay , Rui-Ray Zhang

For a graph representation of a dataset, a straightforward normality measure for a sample can be its graph degree. Considering a weighted graph, degree of a sample is the sum of the corresponding row's values in a similarity matrix. The…

机器学习 · 计算机科学 2018-02-06 Caglar Aytekin , Francesco Cricri , Lixin Fan , Emre Aksu

In this paper, we provide exact formulas for the Castelnuovo-Mumford regularity of powers of an almost complete intersection ideal $I$ which is generated by a homogeneous $d$-sequence. As applications, when $I$ is an almost complete…

交换代数 · 数学 2021-12-01 Yi-Huang Shen , Guangjun Zhu

The Wiener index of a (hyper)graph is calculated by summing up the distances between all pairs of vertices. We determine the maximum possible Wiener index of a connected $n$-vertex $k$-uniform hypergraph and characterize for every~$n$ all…

组合数学 · 数学 2023-02-20 Stijn Cambie , Ervin Győri , Nika Salia , Casey Tompkins , James Tuite

Euler graphs are characterized by the simple criterion that degree of each node is even. By restricting on the cycle types yet additional intrinsic properties of Euler graphs are unveiled. For example, regularity higher than degree two is…

组合数学 · 数学 2020-06-09 Suryaprakash Nagoji Rao

The aim of this paper is to start a systematic investigation of the arithmetic degree of projective schemes as introduced by D. Bayer and D. Mumford. One main theme concerns itself with the behaviour of this arithmetic degree under…

alg-geom · 数学 2008-02-03 Chikashi Miyazaki , Wolfgang Vogel

Let $G$ be a finite simple graph. We give a lower bound for the Castelnuovo-Mumford regularity of the toric ideal $I_G$ associated to $G$ in terms of the sizes and number of induced complete bipartite graphs in $G$. When $G$ is a chordal…

交换代数 · 数学 2016-05-24 Jennifer Biermann , Augustine O'Keefe , Adam Van Tuyl

We define a new combinatorial object, which we call a labeled hypergraph, uniquely associated to any square-free monomial ideal. We prove several upper bounds on the regularity of a square-free monomial ideal in terms of simple…

交换代数 · 数学 2013-04-02 Kuei-Nuan Lin , Jason McCullough

The Castelnuovo-Mumford regularity of a module gives a rough measure of its complexity. We bound the regularity of a module given a system of approximating modules whose regularities are known. Such approximations can arise naturally for…

交换代数 · 数学 2012-01-25 Harm Derksen , Jessica Sidman

We determine the Castelnuovo-Mumford regularity of binomial edge ideals of complement reducible graphs (cographs). For cographs with $n$ vertices the maximum regularity grows as $2n/3$. We also bound the regularity by graph theoretic…

交换代数 · 数学 2021-03-11 Thomas Kahle , Jonas Krüsemann

Fix an integer $n \geq 1$, and consider the set of all connected finite simple graphs on $n$ vertices. For each $G$ in this set, let $I(G)$ denote the edge ideal of $G$ in the polynomial ring $R = K[x_1,\ldots,x_n]$. We initiate a study of…

组合数学 · 数学 2020-03-18 Takayuki Hibi , Kyouko Kimura , Kazunori Matsuda , Adam Van Tuyl

Let X* be a subset of an affine space A^s, over a finite field K, which is parameterized by the edges of a clutter. Let X and Y be the images of X* under the maps x --> [x] and x --> [(x,1)] respectively, where [x] and [(x,1)] are points in…

交换代数 · 数学 2013-06-24 Maria Vaz Pinto , Rafael H. Villarreal