Results 101 to 110 of about 8,914 (221)
Circulant Digraphs with Larger Linear Guessing Number and Smaller Degree
MathematicsThe guessing number of a digraph is a new invariant in graph theory raised by S. Riis in 2006 and based on its applications in network coding and boolean circuit complexity theory. In this paper, we present the lower and upper bounds on a guessing number
Aixian Zhang, Keqin Feng
doaj +1 more source
Advances in Mathematics, 1996 The author applies the language of Joyal's species to enumeration problems of digraphs using the machinery of coloured species, see, e.g., the author and \textit{O. Nava} [J. Comb. Theory, Ser. A 64, No. 1, 102-129 (1993; Zbl 0787.05095)]. A species over digraphs is defined as a functor from the category of digraphs to the category of finite sets and ...
openaire +2 more sources
A Min–Max Relation on Dicuts and Dijoins in Weighted Chordal Digraphs
Journal of Graph Theory, Volume 113, Issue 3, Page 462-469, November 2026.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
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Akram B. Attar EXTENSIBILITY OF GRAPHS
مجلة علوم ذي قار, 2019 In this paper, the concepts of extension of a graph(digraph) and the extensible class of graphs(digraphs) have been introduced. The class of connected graphs as well as the class of Hamiltonian graphs which are extensible classes have also been proved ...
Akram Attar
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Discrete Mathematics, 2006 Let $Φ(x,y)$ be a bivariate polynomial with complex coefficients. The zeroes of $Φ(x,y)$ are given a combinatorial structure by considering them as arcs of a directed graph $G(Φ)$. This paper studies some relationship between the polynomial $Φ(x,y)$ and the structure of $G(Φ)$.
Josep M. Brunat, Antonio Montes
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On the Hardness of Switching to a Small Number of Edges
Journal of Graph Theory, Volume 113, Issue 2, Page 237-251, October 2026.ABSTRACT Seidel's switching is a graph operation which makes a given vertex adjacent to precisely those vertices to which it was non‐adjacent before, while keeping the rest of the graph unchanged. Two graphs are called switching‐equivalent if one can be made isomorphic to the other one by a sequence of switches. Jelínková et al. [DMTCS 13, no. 2, 2011]
Vít Jelínek +2 more
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Halin's Grid Theorem for Digraphs
Journal of Graph Theory, Volume 113, Issue 1, Page 97-112, September 2026.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 of disjoint equivalent out‐rays there is a grid whose vertical rays are contained in ℛ
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On Tight Tree‐Complete Hypergraph Ramsey Numbers
Journal of Graph Theory, Volume 113, Issue 1, Page 88-96, September 2026.ABSTRACT Chvátal showed that for any tree T with k edges, the Ramsey number R ( T , n ) = k ( n − 1 ) + 1. For r = 3 or 4, we show that, if T is an r‐uniform nontrivial tight tree, then the hypergraph Ramsey number R ( T , n ) = Θ ( n r − 1 ). The 3‐uniform result comes from observing a construction of Cooper and Mubayi.
Jiaxi Nie
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On chordal digraphs and semi-strict chordal digraphs [PDF]
, 2019 Chordal graphs are an important class of perfect graphs. The beautiful theory surrounding their study varies from natural applications to elegant characterizations in terms of forbidden subgraphs, subtree representations, vertex orderings, and to ...
Ye, Ying Ying
core
Zero Divisors among Digraphs [PDF]
, 2010 This thesis generalizes to digraphs certain recent results about graphs. There are special digraphs C such that AxC is isomorphic to BxC for some pair of distinct digraphs A and B.
Smith, Heather Christina
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