A Linear Kernel for Planar Total Dominating Set

A total dominating set of a graph $G=(V,E)$ is a subset $D \subseteq V$ such that every vertex in $V$ is adjacent to some vertex in $D$. Finding a total dominating set of minimum size is NP-hard on planar graphs and W[2]-complete on general graphs when parameterized by the solution size. By the meta-theorem of Bodlaender et al. [J. ACM, 2016], there exists a linear kernel for Total Dominating Set on graphs of bounded genus. Nevertheless, it is not clear how such a kernel can be effectively constructed, and how to obtain explicit reduction rules with reasonably small constants. Following the approach of Alber et al. [J. ACM, 2004], we provide an explicit kernel for Total Dominating Set on planar graphs with at most $410k$ vertices, where $k$ is the size of the solution. This result complements several known constructive linear kernels on planar graphs for other domination problems such as Dominating Set, Edge Dominating Set, Efficient Dominating Set, Connected Dominating Set, or Red-Blue Dominating Set.Comment: 33 pages, 13 figure

Defective and Clustered Graph Colouring

Consider the following two ways to colour the vertices of a graph where the requirement that adjacent vertices get distinct colours is relaxed. A colouring has "defect" $d$ if each monochromatic component has maximum degree at most $d$. A colouring has "clustering" $c$ if each monochromatic component has at most $c$ vertices. This paper surveys research on these types of colourings, where the first priority is to minimise the number of colours, with small defect or small clustering as a secondary goal. List colouring variants are also considered. The following graph classes are studied: outerplanar graphs, planar graphs, graphs embeddable in surfaces, graphs with given maximum degree, graphs with given maximum average degree, graphs excluding a given subgraph, graphs with linear crossing number, linklessly or knotlessly embeddable graphs, graphs with given Colin de Verdi\`ere parameter, graphs with given circumference, graphs excluding a fixed graph as an immersion, graphs with given thickness, graphs with given stack- or queue-number, graphs excluding $K_t$ as a minor, graphs excluding $K_{s,t}$ as a minor, and graphs excluding an arbitrary graph $H$ as a minor. Several open problems are discussed.Comment: This is a preliminary version of a dynamic survey to be published in the Electronic Journal of Combinatoric

Self-complementary Graphs

Samokomplementarni grafovi su zanimljivi jer čine beskonačnu klasu grafova i imaju jaka strukturna svojstva. Na primjer, samokomplementaran graf mora imati točno $\frac{n(n-1)}{4}$ bridova, radijus 2, dijametar 2 ili 3 i oni postoje za sve izvodive n. U radu su predstavljeni rezultati brojnih matematičara koji su proučavali samokomplementarne grafove u proteklih 50 godina. Vidjeli smo da su neki od njih korisniji pri dokazivanju da graf nije samokomplementaran. Zapravo, ne postoji jednostavan način kojim bismo dokazali da je neki graf samokomplementaran. Kod ovakvih grafova problem predstavalja ne samo njihovo prepoznavanje, nego općenito brojnost i međusobna izomorfnost.Self-complementary graphs are interesting because they form an infnite class of graphs and have strong structural properties. For example, self-complementary graphs must have exactly $\frac{n(n-1)}{4}$ edges, radius 2 and diameter 2 or 3 and they exist for every feasible value n. In this paper we present results discovered by the mathematicians who studied self-complementary graphs during the last 50 years. We have shown that some of them are more useful in proving that some graph is not self-complementary rather than it is self-complementary. In fact, there is no an easy way to prove that graph is self-complementary. The problem is not just in recognision of those graphs, but also in their number and mutual isomorphism

An extensive English language bibliography on graph theory and its applications

Bibliography on graph theory and its application

Theoretical Computer Science and Discrete Mathematics

This book includes 15 articles published in the Special Issue "Theoretical Computer Science and Discrete Mathematics" of Symmetry (ISSN 2073-8994). This Special Issue is devoted to original and significant contributions to theoretical computer science and discrete mathematics. The aim was to bring together research papers linking different areas of discrete mathematics and theoretical computer science, as well as applications of discrete mathematics to other areas of science and technology. The Special Issue covers topics in discrete mathematics including (but not limited to) graph theory, cryptography, numerical semigroups, discrete optimization, algorithms, and complexity