
arXiv: 1604.00888
AbstractWe present a tight extremal threshold for the existence of Hamilton cycles in graphs with large minimum degree and without a large “bipartite hole” (two disjoint sets of vertices with no edges between them). This result extends Dirac's classical theorem, and is related to a theorem of Chvátal and Erdős. In detail, an ‐bipartite‐hole in a graph G consists of two disjoint sets of vertices S and T with and such that there are no edges between S and T; and is the maximum integer r such that G contains an ‐bipartite‐hole for every pair of nonnegative integers s and t with . Our central theorem is that a graph G with at least three vertices is Hamiltonian if its minimum degree is at least . From the proof we obtain a polynomial time algorithm that either finds a Hamilton cycle or a large bipartite hole. The theorem also yields a condition for the existence of k edge‐disjoint Hamilton cycles. We see that for dense random graphs , the probability of failing to contain many edge‐disjoint Hamilton cycles is . Finally, we discuss the complexity of calculating and approximating .
bipartite hole, Eulerian and Hamiltonian graphs, Extremal problems in graph theory, Random graphs (graph-theoretic aspects), extremal graph theory, Vertex degrees, Hamilton cycle, FOS: Mathematics, Computational difficulty of problems (lower bounds, completeness, difficulty of approximation, etc.), Mathematics - Combinatorics, Combinatorics (math.CO), random graphs
bipartite hole, Eulerian and Hamiltonian graphs, Extremal problems in graph theory, Random graphs (graph-theoretic aspects), extremal graph theory, Vertex degrees, Hamilton cycle, FOS: Mathematics, Computational difficulty of problems (lower bounds, completeness, difficulty of approximation, etc.), Mathematics - Combinatorics, Combinatorics (math.CO), random graphs
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