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In 1973, Erd\H{o}s and Simonovits asked whether every $n$-vertex triangle-free graph with minimum degree greater than $1/3 \cdot n$ is 3-colourable. This question initiated the study of the chromatic profile of triangle-free graphs: for…

Combinatorics · Mathematics 2023-08-22 Freddie Illingworth

For a positive integer $k$, a $k$-colouring of a graph $G=(V,E)$ is a mapping $c: V\rightarrow\{1,2,...,k\}$ such that $c(u)\neq c(v)$ whenever $uv\in E$. The Colouring problem is to decide, for a given $G$ and $k$, whether a $k$-colouring…

Computational Complexity · Computer Science 2016-02-16 Petr A. Golovach , Matthew Johnson , Daniël Paulusma , Jian Song

Local Irregularity Conjecture states that every simple connected graph, except special cacti, can be decomposed into at most three locally irregular graphs, i.e., graphs in which adjacent vertices have different degrees. The connected…

Combinatorics · Mathematics 2025-02-13 Igor Grzelec , Alfréd Onderko , Mariusz Woźniak

The locality of a graph problem is the smallest distance $T$ such that each node can choose its own part of the solution based on its radius-$T$ neighborhood. In many settings, a graph problem can be solved efficiently with a distributed or…

Distributed, Parallel, and Cluster Computing · Computer Science 2021-12-14 Yi-Jun Chang , Jan Studený , Jukka Suomela

For graph classes $P_1,...,P_k$, Generalized Graph Coloring is the problem of deciding whether the vertex set of a given graph $G$ can be partitioned into subsets $V_1,...,V_k$ so that $V_j$ induces a graph in the class $P_j$…

Combinatorics · Mathematics 2007-05-23 Vladimir E. Alekseev , Alastair Farrugia , Vadim V. Lozin

We consider the distributed message-passing {LOCAL} model. In this model a communication network is represented by a graph where vertices host processors, and communication is performed over the edges. Computation proceeds in synchronous…

Distributed, Parallel, and Cluster Computing · Computer Science 2012-05-01 Leonid Barenboim

Let $G$ be a graph on $n$ vertices and let $\mathcal{L}_k$ be an arbitrary function that assigns each vertex in $G$ a list of $k$ colours. Then $G$ is $\mathcal{L}_k$-list colourable if there exists a proper colouring of the vertices of $G$…

Combinatorics · Mathematics 2014-03-12 Jeannette Janssen , Rogers Mathew , Deepak Rajendraprasad

A graph H is common if the number of monochromatic copies of H in a 2-edge-coloring of the complete graph is asymptotically minimized by the random coloring. The classification of common graphs is one of the most intriguing problems in…

Combinatorics · Mathematics 2022-04-28 Robert Hancock , Daniel Kral , Matjaz Krnc , Jan Volec

NP-complete problems should be hard on some instances but those may be extremely rare. On generic instances many such problems, especially related to random graphs, have been proven easy. We show the intractability of random instances of a…

Computational Complexity · Computer Science 2018-10-25 Leonid A. Levin , Ramarathnam Venkatesan

In the List $k$-Coloring problem we are given a graph whose every vertex is equipped with a list, which is a subset of $\{1,\ldots,k\}$. We need to decide if $G$ admits a proper coloring, where every vertex receives a color from its list.…

Combinatorics · Mathematics 2025-09-29 Marta Piecyk , Paweł Rzążewski

A number of recent papers -- e.g. Brandt et al. (STOC 2016), Chang et al. (FOCS 2016), Ghaffari & Su (SODA 2017), Brandt et al. (PODC 2017), and Chang & Pettie (FOCS 2017) -- have advanced our understanding of one of the most fundamental…

Distributed, Parallel, and Cluster Computing · Computer Science 2018-04-06 Alkida Balliu , Juho Hirvonen , Janne H. Korhonen , Tuomo Lempiäinen , Dennis Olivetti , Jukka Suomela

In this work, we develop the low-space Massively Parallel Computation (MPC) complexity landscape for a family of fundamental graph problems on trees. We present a general method that solves most locally checkable labeling (LCL) problems…

Distributed, Parallel, and Cluster Computing · Computer Science 2022-03-04 Sebastian Brandt , Rustam Latypov , Jara Uitto

Using the algebraic approach to promise constraint satisfaction problems, we establish complexity classifications of three natural variants of hypergraph colourings: standard nonmonochromatic colourings, conflict-free colourings, and…

Discrete Mathematics · Computer Science 2026-05-01 Tamio-Vesa Nakajima , Zephyr Verwimp , Marcin Wrochna , Stanislav Živný

A lambda colouring (or $L(2,1)-$colouring) of a graph is an assignment of non-negative integers (with minimum assignment $0$) to its vertices such that the adjacent vertices must receive integers at least two apart and vertices at distance…

Combinatorics · Mathematics 2019-01-07 Kaushik Majumder , Ushnish Sarkar

A proper vertex coloring of a graph is said to be locally identifying if the sets of colors in the closed neighborhood of any two adjacent non-twin vertices are distinct. The lid-chromatic number of a graph is the minimum number of colors…

Combinatorics · Mathematics 2013-07-11 Daniel Gonçalves , Aline Parreau , Alexandre Pinlou

A \textit{locally identifying coloring} ($lid$-coloring) of a graph is a proper coloring such that the sets of colors appearing in the closed neighborhoods of any pair of adjacent vertices having distinct neighborhoods are distinct. Our…

Combinatorics · Mathematics 2014-06-17 Méziane Aïder , Sylvain Gravier , Souad Slimani

The $\Delta$-vertex coloring problem has become one of the prototypical problems for understanding the complexity of local distributed graph problems on constant-degree graphs. The major open problem is whether the problem can be solved…

Distributed, Parallel, and Cluster Computing · Computer Science 2025-04-08 Manuel Jakob , Yannic Maus

Graph coloring is one of the most famous computational problems with applications in a wide range of areas such as planning and scheduling, resource allocation, and pattern matching. So far coloring problems are mostly studied on static…

Discrete Mathematics · Computer Science 2019-06-12 George B. Mertzios , Hendrik Molter , Viktor Zamaraev

In this paper, we study the notion of mending, i.e. given a partial solution to a graph problem, we investigate how much effort is needed to turn it into a proper solution. For example, if we have a partial coloring of a graph, how hard is…

Distributed, Parallel, and Cluster Computing · Computer Science 2022-09-13 Darya Melnyk , Jukka Suomela , Neven Villani

A Locally Checkable Labeling (LCL) is a specification describing a set of labels that are valid with respect to a set of conditions that characterize a local part of a solution to a global problem. Conditions can only refer to nodes and…

Distributed, Parallel, and Cluster Computing · Computer Science 2026-02-17 Jérémie Chalopin , Maria Kokkou