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A graph $G$ is total weight $(k,k')$-choosable if for any total list assignment $L$ which assigns to each vertex $v$ a set $L(v)$ of $k$ real numbers, and each edge $e$ a set $L(e)$ of $k'$ real numbers, there is a proper total…

Combinatorics · Mathematics 2022-02-22 Huajing Lu , Xuding Zhu

A $(d,h)$-decomposition of a graph $G$ is an ordered pair $(D, H)$ such that $H$ is a subgraph of $G$ of maximum degree at most $h$ and $D$ is an acyclic orientation of $G-E(H)$ with maximum out-degree at most $d$. In this paper, we prove…

Combinatorics · Mathematics 2023-03-16 Lingxi Li , Huajing Lu , Tao Wang , Xuding Zhu

We prove that if $p\ge n^{-\frac{1}{3}+\beta}$ for some $\beta > 0$, then asymptotically almost surely the binomial random graph $G(n,p)$ has a $K_3$-packing containing all but at most $n + O(1)$ edges. Similarly, we prove that if $d \ge…

Combinatorics · Mathematics 2024-02-29 Michelle Delcourt , Tom Kelly , Luke Postle

In this paper, we give a class of reconstructible graphs.

Combinatorics · Mathematics 2007-05-23 Tetsuya Hosaka

Given a graph $G=([n],E)$ and $w\in\R^E$, consider the integer program ${\max}_{x\in \{\pm 1\}^n} \sum_{ij \in E} w_{ij}x_ix_j$ and its canonical semidefinite programming relaxation ${\max} \sum_{ij \in E} w_{ij}v_i^Tv_j$, where the maximum…

Combinatorics · Mathematics 2011-06-15 Monique Laurent , Antonios Varvitsiotis

A graph $G$ is $k$-vertex-critical if $G$ has chromatic number $k$ but every proper induced subgraph of $G$ has chromatic number less than $k$. The study of $k$-vertex-critical graphs for graph classes is an important topic in algorithmic…

Combinatorics · Mathematics 2021-08-21 Qingqiong Cai , Jan Goedgebeur , Shenwei Huang

A graph G is (a:b)-colorable if there exists an assignment of b-element subsets of {1,...,a} to vertices of G such that sets assigned to adjacent vertices are disjoint. We show that every planar graph without cycles of length 4 or 5 is…

Combinatorics · Mathematics 2019-07-16 Zdeněk Dvořák , Xiaolan Hu

A graph $G$ is called \emph{chromatic-choosable} if its choice number is equal to its chromatic number, namely $Ch(G)=\chi(G)$. Ohba has conjectured that every graph $G$ satisfying $|V(G)|\leq 2\chi(G)+1$ is chromatic-choosable. Since each…

Combinatorics · Mathematics 2015-08-06 Wenjie He , Lingmin Zhang , Daniel W. Cranston , Yufa Shen , Guoping Zheng

A decomposition of a graph $G$ is a family of subgraphs of $G$ whose edge sets form a partition of $E(G)$. In this paper, we prove that every triangle-free planar graph $G$ can be decomposed into a $2$-degenerate graph and a matching.…

Combinatorics · Mathematics 2022-12-15 Rongxing Xu , Xuding Zhu

We describe computer searches that prove the graph reconstruction conjecture for graphs with up to 13 vertices and some limited classes on larger sizes. We also investigate the reconstructibility of tournaments up to 13 vertices, digraphs…

Combinatorics · Mathematics 2022-01-04 Brendan D. McKay

We prove that a large family of graphs which are decomposable with respect to the modular decomposition can be reconstructed from their collection of vertex-deleted subgraphs.

Combinatorics · Mathematics 2012-02-28 Robert Brignall , Nicholas Georgiou , Robert J. Waters

Goedgebeur and Schaudt [J. Graph Theory 87 (2018) 188-207] conjectured that all 4-vertex-critical $(P_7,C_3)$-free graphs belongs to the family $\cal G$, which consists of seven explicitly defined graphs. In this paper, we establish a…

Combinatorics · Mathematics 2026-03-24 Ran Chen , Di Wu , Xiaowen Zhang

The reconfiguration graph of the $k$-colorings, denoted $R_k(G)$, is the graph whose vertices are the $k$-colorings of $G$ and two colorings are adjacent in $R_k(G)$ if they differ in color on exactly one vertex. A graph $G$ is said to be…

Combinatorics · Mathematics 2024-11-13 Manoj Belavadi , Kathie Cameron

The $d$-dimensional algebraic connectivity $a_d(G)$ of a graph $G=(V,E)$ is a quantitative measure of its $d$-dimensional rigidity, defined in terms of the eigenvalues of stiffness matrices associated with different embeddings of the graph…

Combinatorics · Mathematics 2025-04-03 Yunseong Jung , Alan Lew

Let $G$ be a connected graph and $\mathcal{P}(G)$ a graph parameter. We say that $\mathcal{P}(G)$ is feasible if $\mathcal{P}(G)$ satisfies the following properties: (I) $\mathcal{P}(G)\leq \mathcal{P}(G_{uv})$, if $G_{uv}=G[u\to v]$ for…

Combinatorics · Mathematics 2026-04-09 Jiangdong Ai , Hui Lei , Bo Ning , Yongtang Shi

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 ${\rm dim}(G)$ and $D(G)$ respectively denote the metric dimension and the distinguishing number of a graph $G$. It is proved that $D(G) \le {\rm dim}(G)+1$ holds for every connected graph $G$. Among trees, exactly paths and stars…

Combinatorics · Mathematics 2025-07-08 Meysam Korivand , Nasrin Soltankhah , Sandi Klavžar

In this paper, we prove that there exists an absolute constant $g_0$ such that, for every integer $k\ge 3$, every graph $G$ with $\delta(G)\ge k$ and $g(G)\ge g_0$ contains an induced subdivision of $K_{k+1}$. This answers, in a strong…

Combinatorics · Mathematics 2026-05-19 Peiru Kuang , Yan Wang

We construct a new family of strongly regular graphs with the same parameters as the strongly regular graphs $D_{5,5}(q)$. The construction can be seen as a variant of the construction of twisted Grassmann graphs by Van Dam and Koolen.

Combinatorics · Mathematics 2024-01-12 Ferdinand Ihringer

Let G = (V, E) be a directed graph on n vertices where each vertex has out-degree k. We say that G is kNN-realizable in d-dimensional Euclidean space if there exists a point set P = {p1, p2, ..., pn} in R^d along with a one-to-one mapping…

Computational Geometry · Computer Science 2025-04-10 T. Schibler , S. Suri , J. Xue