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A semicomplete digraph is a quasi-transitive digraph. There are extensions of quasi-transitive digraphs called k-quasi-transitive digraphs. [5] Oriented graphs are directed graphs having no opposite pairs of directed edges (i.e. at most one of (x, y) and (y, x) may be arrows of the graph).
A signed digraph is a directed graph with signed arcs. Signed digraphs are far more complicated than signed graphs, because only the signs of directed cycles are significant. For instance, there are several definitions of balance, each of which is hard to characterize, in strong contrast with the situation for signed undirected graphs.
The reconstruction conjecture of Stanisław Ulam is one of the best-known open problems in graph theory.Using the terminology of Frank Harary [1] it can be stated as follows: If G and H are two graphs on at least three vertices and ƒ is a bijection from V(G) to V(H) such that G\{v} and H\{ƒ(v)} are isomorphic for all vertices v in V(G), then G and H are isomorphic.
In Welsh, the digraph ll fused for a time into a ligature.. A digraph (from Ancient Greek δίς (dís) 'double' and γράφω (gráphō) 'to write') or digram is a pair of characters used in the orthography of a language to write either a single phoneme (distinct sound), or a sequence of phonemes that does not correspond to the normal values of the two characters combined.
The best known vertex transitive digraphs (as of October 2008) in the directed Degree diameter problem are tabulated below. Table of the orders of the largest known vertex-symmetric graphs for the directed degree diameter problem
Most adults with dyscalculia have a hard time processing math at a 4th-grade level. For 1st–4th grade level, many adults will know what to do for the math problem, but they will often get them wrong because of "careless errors", although they are not careless when it comes to the problem.
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In mathematics, the free category or path category generated by a directed graph or quiver is the category that results from freely concatenating arrows together, whenever the target of one arrow is the source of the next. More precisely, the objects of the category are the vertices of the quiver, and the morphisms are paths between objects.