Results 41 to 50 of about 28,427 (196)
On (4,2)-digraph Containing a Cycle of Length 2 [PDF]
, 2000 A diregular digraph is a digraph with the in-degree and out-degree of all vertices is constant. The Moore bound for a diregular digraph of degree d and diameter k is M_{d,k}=l+d+d^2+...+d^k.
Baskoro, Edy Tri, Iswadi, Hazrul
core
Optimal segmentation of directed graph and the minimum number of feedback arcs
, 2017 The minimum feedback arc set problem asks to delete a minimum number of arcs (directed edges) from a digraph (directed graph) to make it free of any directed cycles.
Xu, Yi-Zhi, Zhou, Hai-Jun
core +1 more source
Upper Bounds on the Minimum Size of Feedback Arc Set of Directed Multigraphs With Bounded Degree
Journal of Graph Theory, EarlyView.ABSTRACT An oriented multigraph is a directed multigraph without directed 2‐cycles. Let fas ( D ) $\text{fas}(D)$ denote the minimum size of a feedback arc set in an oriented multigraph D $D$. In several papers, upper bounds for fas ( D ) $\text{fas}(D)$ were obtained for oriented multigraphs D $D$ with maximum degree upper‐bounded by a constant ...
Gregory Gutin +3 more
wiley +1 more source
Algebra universalisAbstract Call a finite relational structure k-Słupecki if its only surjective k -ary polymorphisms are essentially unary, and Słupecki if it is k -Słupecki
Kunos, Ádám +2 more
openaire +2 more sources
Halin's Grid Theorem for Digraphs
Journal of Graph Theory, EarlyView.ABSTRACT Halin showed that every thick end of every graph contains an infinite grid. We extend Halin's theorem to digraphs. More precisely, we show that for every infinite family ℛ ${\rm{ {\mathcal R} }}$ of disjoint equivalent out‐rays there is a grid whose vertical rays are contained in ℛ ${\rm{ {\mathcal R} }}$.
Florian Reich
wiley +1 more source
On Tight Tree‐Complete Hypergraph Ramsey Numbers
Journal of Graph Theory, EarlyView.ABSTRACT Chvátal showed that for any tree T $T$ with k $k$ edges, the Ramsey number R ( T , n ) = k ( n − 1 ) + 1 $R(T,n)=k(n-1)+1$. For r = 3 $r=3$ or 4, we show that, if T $T$ is an r $r$‐uniform nontrivial tight tree, then the hypergraph Ramsey number R ( T , n ) = Θ ( n r − 1 ) $R(T,n)={\rm{\Theta }}({n}^{r-1})$.
Jiaxi Nie
wiley +1 more source
Some Remarks On The Structure Of Strong K-Transitive Digraphs
Discussiones Mathematicae Graph Theory, 2014 A digraph D is k-transitive if the existence of a directed path (v0, v1, . . . , vk), of length k implies that (v0, vk) ∈ A(D). Clearly, a 2-transitive digraph is a transitive digraph in the usual sense.
Hernández-Cruz César +1 more
doaj +1 more source
Extremal Digraphs Avoiding Distinct Walks of Length 4 with the Same Endpoints
Discussiones Mathematicae Graph Theory, 2022 Let n ≥ 8 be an integer. We characterize the extremal digraphs of order n with the maximum number of arcs avoiding distinct walks of length 4 with the same endpoints.
Lyu Zhenhua
doaj +1 more source
Orbits of rotor-router operation and stationary distribution of random walks on directed graphs
, 2015 The rotor-router model is a popular deterministic analogue of random walk. In this paper we prove that all orbits of the rotor-router operation have the same size on a strongly connected directed graph (digraph) and give a formula for the size.
Van Pham, Trung
core +1 more source
Orientations of Graphs With at Most One Directed Path Between Every Pair of Vertices
Journal of Graph Theory, EarlyView.ABSTRACT Given a graph G $G$, we say that an orientation D $D$ of G $G$ is a KT orientation if, for all u , v ∈ V ( D ) $u,v\in V(D)$, there is at most one directed path (in any direction) between u $u$ and v $v$. Graphs that admit such orientations have been used to construct graphs with large chromatic number and small clique number that served as ...
Barbora Dohnalová +3 more
wiley +1 more source