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  2. Logic of graphs - Wikipedia

    en.wikipedia.org/wiki/Logic_of_graphs

    These thresholds can never be an irrational power of , so random graphs where the edge inclusion probability is an irrational power obey a zero-one law analogous to the one for uniformly random graphs. A similar zero-one law holds for very sparse random graphs that have an edge inclusion probability of with >, as long as is not a ...

  3. Probabilistic method - Wikipedia

    en.wikipedia.org/wiki/Probabilistic_method

    Here comes the trick: since G has these two properties, we can remove at most n/2 vertices from G to obtain a new graph G′ on ′ / vertices that contains only cycles of length at least g. We can see that this new graph has no independent set of size ⌈ n ′ k ⌉ {\displaystyle \left\lceil {\frac {n'}{k}}\right\rceil } .

  4. Orientation (graph theory) - Wikipedia

    en.wikipedia.org/wiki/Orientation_(graph_theory)

    A directed graph is called an oriented graph if none of its pairs of vertices is linked by two mutually symmetric edges. Among directed graphs, the oriented graphs are the ones that have no 2-cycles (that is at most one of (x, y) and (y, x) may be arrows of the graph). [1] A tournament is an orientation of a complete graph.

  5. Second neighborhood problem - Wikipedia

    en.wikipedia.org/wiki/Second_neighborhood_problem

    A vertex in a directed graph whose second neighborhood is at least as large as its first neighborhood is called a Seymour vertex. [5]In the second neighborhood conjecture, the condition that the graph have no two-edge cycles is necessary, for in graphs that have such cycles (for instance the complete oriented graph) all second neighborhoods may be empty or small.

  6. Mixed graph - Wikipedia

    en.wikipedia.org/wiki/Mixed_graph

    Mixed graphs are also used as graphical models for Bayesian inference. In this context, an acyclic mixed graph (one with no cycles of directed edges) is also called a chain graph. The directed edges of these graphs are used to indicate a causal connection between two events, in which the outcome of the first event influences the probability of ...

  7. Graph (discrete mathematics) - Wikipedia

    en.wikipedia.org/wiki/Graph_(discrete_mathematics)

    A graph with three vertices and three edges. A graph (sometimes called an undirected graph to distinguish it from a directed graph, or a simple graph to distinguish it from a multigraph) [4] [5] is a pair G = (V, E), where V is a set whose elements are called vertices (singular: vertex), and E is a set of unordered pairs {,} of vertices, whose elements are called edges (sometimes links or lines).

  8. Glossary of graph theory - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_graph_theory

    2. The Frucht graph, one of the two smallest cubic graphs with no nontrivial symmetries. 3. Frucht's theorem that every finite group is the group of symmetries of a finite graph. full Synonym for induced. functional graph A functional graph is a directed graph where every vertex has out-degree one. Equivalently, a functional graph is a maximal ...

  9. Connectivity (graph theory) - Wikipedia

    en.wikipedia.org/wiki/Connectivity_(graph_theory)

    This graph becomes disconnected when the right-most node in the gray area on the left is removed This graph becomes disconnected when the dashed edge is removed.. In mathematics and computer science, connectivity is one of the basic concepts of graph theory: it asks for the minimum number of elements (nodes or edges) that need to be removed to separate the remaining nodes into two or more ...