منابع مشابه
An Infinite Highly Arc-transitive Digraph
The main purpose of this note is to construct an infinite , highly arc-transitive digraph with finite out-valency , and with out-spread greater than 1 , which does not have the two-way infinite path Z as a homomorphic image . This answers Question 3 . 8 in the paper [3] of Cameron , Praeger and Wormald . Our digraph has infinite in-valency . By a result of Praeger (see [5]) , a connected , vert...
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In a digraph D = (X,U) , not necessarily finite, an arc (x, y) ∈ U is reachable from a vertex u if there exists a directed walk W that originates from u and contains (x, y) . A subset S ⊆ X is an arc-reaching set of D if for every arc (x, y) there exists a diwalk W originating at a vertex u ∈ S and containing (x, y) . A minimal arc-reaching set is an arc-basis. S is a point-reaching set if for ...
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The concepts of root tree, the set of successors of a node in decorated tree and sets of subtrees are introduced. Let us mention that every tree which is finite is also finite-order. Next we state three propositions: (1) For every decorated tree t holds tε N = t. (2) For every tree t and for all finite sequences p, q of elements of N such that p q ∈ t holds t(p q) = tpq. (3) Let t be a decorate...
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ژورنال
عنوان ژورنال: Journal of Combinatorial Theory
سال: 1967
ISSN: 0021-9800
DOI: 10.1016/s0021-9800(67)80101-7