On prisms, Möbius ladders and the cycle space of dense graphs

  • Authors:
  • Peter Heinig

  • Affiliations:
  • -

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2014

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Abstract

For a graph G, let |G| denote its number of vertices, @d(G) its minimum degree and Z"1(G;F"2) its cycle space. Call a graph Hamilton-generated if and only if every cycle in G is a symmetric difference of some Hamilton circuits of G. The main purpose of this paper is to prove: for every @c0 there exists n"0@?Z such that for every graph G with |G|=n"0 vertices, (1)if @d(G)=(12+@c)|G| and |G| is odd, then G is Hamilton-generated, (2)if @d(G)=(12+@c)|G| and |G| is even, then the set of all Hamilton circuits of G generates a codimension-one subspace of Z"1(G;F"2) and the set of all circuits of G having length either |G|-1 or |G| generates all of Z"1(G;F"2), (3)if @d(G)=(14+@c)|G| and G is balanced bipartite, then G is Hamilton-generated. All these degree-conditions are essentially best-possible. The implications in (1) and (2) give an asymptotic affirmative answer to a special case of an open conjecture which according to [I.B.-A. Hartman, Long cycles generate the cycle space of a graph, European J. Combin. 4 (3) (1983) 237-246] originates with A. Bondy.