Results 91 to 100 of about 34,890 (227)
On Endomorphism Universality of Sparse Graph Classes
Journal of Graph Theory, Volume 110, Issue 2, Page 223-244, October 2025.ABSTRACT We show that every commutative idempotent monoid (a.k.a. lattice) is the endomorphism monoid of a subcubic graph. This solves a problem of Babai and Pultr and the degree bound is best‐possible. On the other hand, we show that no class excluding a minor can have all commutative idempotent monoids among its endomorphism monoids. As a by‐product,
Kolja Knauer, Gil Puig i Surroca
wiley +1 more source
On the Cayley digraphs that are patterns of unitary matrices
, 2002 A digraph D is the pattern of a matrix M when D has an arc ij if and only if the ij-th entry of M is nonzero. Study the relationship between unitary matrices and their patterns is motivated by works in quantum chaology and quantum computation.
Severini, Simone
core +1 more source
A Dichotomy Theorem for Γ‐Switchable H‐Colouring on m‐Edge‐Coloured Graphs
Journal of Graph Theory, Volume 110, Issue 2, Page 200-208, October 2025.ABSTRACT Let G be a graph in which each edge is assigned one of the colours 1 , 2 , … , m, and let Γ be a subgroup of S m. The operation of switching at a vertex x of G with respect to an element π of Γ permutes the colours of the edges incident with x according to π.
Richard Brewster +2 more
wiley +1 more source
Precedence‐Constrained Shortest Path
Networks, Volume 86, Issue 3, Page 282-295, October 2025.ABSTRACT We propose a variant of the shortest path problem where the order in which vertices occur in the path is subject to precedence constraints. Precedence constraints are defined in terms of vertex pairs (a,b)$$ \left(a,b\right) $$ which indicate that a vertex a$$ a $$ is the predecessor of a vertex b$$ b $$.
Christina Büsing +2 more
wiley +1 more source
Infinite kernel perfect digraphs
AKCE International Journal of Graphs and Combinatorics, 2017 Let be a digraph, possibly infinite, V() and A() will denote the sets of vertices and arcs of , respectively. A subset of V() is said to be a kernel if it is both independent (a vertex in has no successor in ) and absorbing (a vertex not in has a ...
Rocío Sánchez-López
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Tree-average distances on certain phylogenetic networks have their weights uniquely determined
Algorithms for Molecular Biology, 2012 A phylogenetic network N has vertices corresponding to species and arcs corresponding to direct genetic inheritance from the species at the tail to the species at the head.
Willson Stephen J
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Tr-Span of Directed Wheel Graphs
Discussiones Mathematicae Graph Theory, 2018 In this paper, we consider T-colorings of directed graphs. In particular, we consider as a T-set the set Tr = {0, 1, 2, . . ., r−1, r+1, . . .}. Exact values and bounds of the Tr-span of directed graphs whose underlying graph is a wheel graph are ...
Besson Marc, Tesman Barry
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Directed graph theory for the analysis of biological regulatory networks
Frontiers in Applied Mathematics and StatisticsSynchronous regulated biological networks are often represented as logical diagrams, where the precise interactions between elements remain obscured. Here, we introduce a novel type of excitation-inhibition graph based on Boolean logic, which we term ...
Martha Takane +8 more
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Unordered Love in infinite directed graphs
International Journal of Mathematics and Mathematical Sciences, 1992 A digraph D=(V,A) has the Unordered Love Property (ULP) if any two different vertices have a unique common outneighbor. If both (V,A) and (V,A−1) have the ULP, we say that D has the SDULP.
Peter D. Johnson
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