Results 61 to 70 of about 4,954 (163)
Countable connected-homogeneous digraphs [PDF]
, 2013 A digraph is connected-homogeneous if every isomorphism between two finite connected induced subdigraphs extends to an automorphism of the whole digraph.
Hamann, Matthias
core
An Infinite Highly Arc-transitive Digraph
European Journal of Combinatorics, 1997 A digraph is highly arc-transitive if its automorphism group is transitive on \(s\)-arcs, for all natural numbers \(s\). In this paper, an infinite, highly arc-transitive digraph with infinite in-valency, finite out-valency, and with out-spread greater than 1, which does not have the two-way infinite path \(Z\) as a homomorphic image, is constructed ...
openaire +1 more source
Quantum automorphism groups of lexicographic products of graphs
Journal of the London Mathematical Society, Volume 111, Issue 4, April 2025.Abstract Sabidussi's theorem [Duke Math. J. 28 (1961), 573–578] gives necessary and sufficient conditions under which the automorphism group of a lexicographic product of two graphs is a wreath product of the respective automorphism groups. We prove a quantum version of Sabidussi's theorem for finite graphs, with the automorphism groups replaced by ...
Arnbjörg Soffía Árnadóttir +4 more
wiley +1 more source
On the Complexity of the 3-Kernel Problem in Some Classes of Digraphs
Discussiones Mathematicae Graph Theory, 2014 Let D be a digraph with the vertex set V (D) and the arc set A(D). A subset N of V (D) is k-independent if for every pair of vertices u, v ∈ N, we have d(u, v), d(v, u) ≥ k; it is l-absorbent if for every u ∈ V (D) − N there exists v ∈ N such that d(u, v)
Hell Pavol, Hernández-Cruz César
doaj +1 more source
Cladistics, Volume 41, Issue 1, Page 1-27, February 2025.Abstract Here, we propose, prove mathematically and discuss maximum and minimum measures of maximum parsimony evolution across 12 discrete phylogenetic character types, classified across 4467 morphological and molecular datasets. Covered character types are: constant, binary symmetric, multistate unordered (non‐additive) symmetric, multistate linear ...
Jennifer F. Hoyal Cuthill +1 more
wiley +1 more source
Strong arc decompositions of split digraphs
Journal of Graph Theory, Volume 108, Issue 1, Page 5-26, January 2025.Abstract A strong arc decomposition of a digraph D = ( V , A ) is a partition of its arc set A into two sets A 1 , A 2 such that the digraph D i = ( V , A i ) is strong for i = 1 , 2. Bang‐Jensen and Yeo conjectured that there is some K such that every K‐arc‐strong digraph has a strong arc decomposition. They also proved that with one exception on four
Jørgen Bang‐Jensen, Yun Wang
wiley +1 more source
Finite $s$-Geodesic-Transitive Digraphs
The Electronic Journal of CombinatoricsThis paper initiates the investigation of the family of $(G,s)$-geodesic-transitive digraphs with $s\geq 2$. We first give a global analysis by providing a reduction result. Let $\Gamma$ be such a digraph and let $N$ be a normal subgroup of $G$ maximal with respect to having at least $3$ orbits.
openaire +2 more sources
Immersions of Directed Graphs in Tournaments
Random Structures &Algorithms, Volume 66, Issue 1, January 2025.ABSTRACT Recently, Draganić, Munhá Correia, Sudakov and Yuster (2022) showed that every tournament on (2+o(1))k2$$ \left(2+o(1)\right){k}^2 $$ vertices contains a 1‐subdivision of a transitive tournament on k$$ k $$ vertices, which is tight up to a constant factor. We prove a counterpart of their result for immersions.
António Girão, Robert Hancock
wiley +1 more source
Colourings, homomorphisms, and partitions of transitive digraphs
European Journal of Combinatorics, 2017 We investigate the complexity of generalizations of colourings (acyclic colourings, $(k,\ell)$-colourings, homomorphisms, and matrix partitions), for the class of transitive digraphs. Even though transitive digraphs are nicely structured, many problems are intractable, and their complexity turns out to be difficult to classify.
Feder, Tomás +2 more
openaire +2 more sources
Journal of Mathematics, Volume 2025, Issue 1, 2025.The construction of circuits formed by reduced quadratic irrational numbers (RQINs) under the action of Mobius groups has attracted growing attention due to their deep algebraic structure and wide range of applications. Such orbits and circuits play a significant role in modern cryptographic systems, particularly in the design of robust substitution ...
Muhammad Haris Mateen +5 more
wiley +1 more source