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  2. Handshaking lemma - Wikipedia

    en.wikipedia.org/wiki/Handshaking_lemma

    However, it is possible to formulate a version of the handshaking lemma using the concept of an end, an equivalence class of semi-infinite paths ("rays") considering two rays as equivalent when there exists a third ray that uses infinitely many vertices from each of them. The degree of an end is the maximum number of edge-disjoint rays that it ...

  3. Double counting (proof technique) - Wikipedia

    en.wikipedia.org/wiki/Double_counting_(proof...

    In more colloquial terms, in a party of people some of whom shake hands, an even number of people must have shaken an odd number of other people's hands; for this reason, the result is known as the handshaking lemma. To prove this by double counting, let () be the degree of vertex . The number of vertex-edge incidences in the graph may be ...

  4. Degree (graph theory) - Wikipedia

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

    The formula implies that in any undirected graph, the number of vertices with odd degree is even. This statement (as well as the degree sum formula) is known as the handshaking lemma. The latter name comes from a popular mathematical problem, which is to prove that in any group of people, the number of people who have shaken hands with an odd ...

  5. Eulerian path - Wikipedia

    en.wikipedia.org/wiki/Eulerian_path

    Handshaking lemma, proven by Euler in his original paper, showing that any undirected connected graph has an even number of odd-degree vertices; Hamiltonian path – a path that visits each vertex exactly once. Route inspection problem, search for the shortest path that visits all edges, possibly repeating edges if an Eulerian path does not exist.

  6. List of lemmas - Wikipedia

    en.wikipedia.org/wiki/List_of_lemmas

    Burnside's lemma also known as the Cauchy–Frobenius lemma; Frattini's lemma (finite groups) Goursat's lemma; Mautner's lemma (representation theory) Ping-pong lemma (geometric group theory) Schreier's subgroup lemma; Schur's lemma (representation theory) Zassenhaus lemma

  7. Hypergraph regularity method - Wikipedia

    en.wikipedia.org/wiki/Hypergraph_regularity_method

    Similarly, the hypergraph counting lemma is a generalization of the graph counting lemma that estimates number of copies of a fixed graph as a subgraph of a larger graph. There are several distinct formulations of the method, all of which imply the hypergraph removal lemma and a number of other powerful results, such as Szemerédi's theorem ...

  8. Psychologists break down the meaning of Donald Trump's handshake

    www.aol.com/news/2017-05-30-psychologists-break...

    Nunberg believes his handshake is indicative of Trump's famous phrase, too. He told Huffington Post, "If we are talking about his handshake, it is kind of analogous to us talking about him when he ...

  9. Chinese postman problem - Wikipedia

    en.wikipedia.org/wiki/Chinese_postman_problem

    The undirected route inspection problem can be solved in polynomial time by an algorithm based on the concept of a T-join.Let T be a set of vertices in a graph. An edge set J is called a T-join if the collection of vertices that have an odd number of incident edges in J is exactly the set T.