Results 61 to 70 of about 5,946 (233)
Stable Cuts, NAC‐Colourings and Flexible Realisations of Graphs
Journal of Graph Theory, EarlyView.ABSTRACT A (2‐dimensional) realisation of a graph G $G$ is a pair ( G , p ) $(G,p)$, where p $p$ maps the vertices of G $G$ to R 2 ${{\mathbb{R}}}^{2}$. A realisation is flexible if it can be continuously deformed while keeping the edge lengths fixed, and rigid otherwise.
Katie Clinch +5 more
wiley +1 more source
Generalized inverses in graph theory
AKCE International Journal of Graphs and Combinatorics, 2023 –In this article, some interesting applications of generalized inverses in the graph theory are revisited. Interesting properties of generalized inverses are employed to make the proof of several known results simpler, and several techniques such as ...
Umashankara Kelathaya +2 more
doaj +1 more source
Linear Versus Centred Colouring via Pseudogrids
Journal of Graph Theory, EarlyView.ABSTRACT A centred colouring of a graph is a vertex colouring in which every connected subgraph contains a vertex whose colour is unique and a linear colouring is a vertex colouring in which every (not‐necessarily induced) path contains a vertex whose colour is unique. For a graph G $G$, the centred chromatic number χ cen ( G ) ${\chi }_{\text{cen}}(G)$
Prosenjit Bose +4 more
wiley +1 more source
Bipartite Diametrical Graphs of Diameter 4 and Extreme Orders
International Journal of Mathematics and Mathematical Sciences, 2008 We provide a process to extend any bipartite diametrical graph of diameter 4 to an 𝑆-graph of the same diameter and partite sets. For a bipartite diametrical graph of diameter 4 and partite sets 𝑈 and 𝑊, where 2𝑚=|𝑈|≤|𝑊|, we prove that 2𝑚 is a sharp ...
Salah Al-Addasi, Hasan Al-Ezeh
doaj +1 more source
On the palette index of complete bipartite graphs
Discussiones Mathematicae Graph Theory, 2018 zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Mirko Hornák, Juraj Hudák
openaire +2 more sources
A Min–Max Relation on Dicuts and Dijoins in Weighted Chordal Digraphs
Journal of Graph Theory, EarlyView.ABSTRACT In a digraph, a dicut is a cut where all the arcs cross in one direction. A dijoin is a subset of arcs that intersects every dicut. Edmonds and Giles conjectured that in a weighted digraph, the minimum weight of a dicut is equal to the maximum size of a packing of dijoins. This has been disproved. However, the unweighted version conjectured by
Gérard Cornuéjols, Siyue Liu, R. Ravi
wiley +1 more source
Density Conditions for k $k$ Vertex‐Disjoint Triangles in Tripartite Graphs
Journal of Graph Theory, EarlyView.ABSTRACT Let n , k $n,k$ be positive integers such that n ≥ k $n\ge k$ and G $G$ be a tripartite graph with parts A , B , C $A,B,C$ such that ∣ A ∣ = ∣ B ∣ = ∣ C ∣ = n $| A| =| B| =| C| =n$. Denote the edge densities of G [ A , B ] , G [ A , C ] $G[A,B],G[A,C]$ and G [ B , C ] $G[B,C]$ by α , β $\alpha ,\beta $ and γ $\gamma $, respectively.
Mingyang Guo, Klas Markström
wiley +1 more source
Journal of Graph Theory, EarlyView.ABSTRACT In an effort to understand the complexity of the maximum independent set problem, Chvátal introduced t‐perfect graphs. While a full characterization of this class remains open, important progress has been made for claw‐free graphs [Bruhn and Stein, Math. Program. 2012] and P 5 ${P}_{5}$‐free graphs [Bruhn and Fuchs, SIAM J. Discrete Math. 2017]
Yixin Cao, Shenghua Wang
wiley +1 more source
Tree Independence Number III. Thetas, Prisms and Stars
Journal of Graph Theory, EarlyView.ABSTRACT We prove that for every t ∈ N $t\in {\mathbb{N}}$ there exists τ = τ ( t ) ∈ N $\tau =\tau (t)\in {\mathbb{N}}$ such that every (theta, prism, K 1 , t ${K}_{1,t}$)‐free graph has tree independence number at most τ $\tau $ (where we allow “prisms” to have one path of length zero).
Maria Chudnovsky +2 more
wiley +1 more source
On Odd Covers of Cliques and Disjoint Unions
Journal of Graph Theory, EarlyView.ABSTRACT Babai and Frankl posed the “odd cover problem” of finding the minimum cardinality of a collection of complete bipartite graphs such that every edge of the complete graph of order n $n$ is covered an odd number of times. In a previous paper with O'Neill, some of the authors proved that this value is always ⌈ n / 2 ⌉ $\lceil n/2\rceil $ or ⌈ n /
Calum Buchanan +7 more
wiley +1 more source