On factors of 4-connected claw-free graphs

Haitze J. Broersma, M. Kriesell, M. Kriesell, Z. Ryjacek

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We consider the existence of several different kinds of factors in 4-connected claw-free graphs. This is motivated by the following two conjectures which are in fact equivalent by a recent result of the third author. Conjecture 1 (Thomassen): Every 4-connected line graph is Hamiltonian, i.e. has a connected 2-factor. Conjecture 2 (Matthews and Sumner): Every 4-connected claw-free graph is hamiltonian. We first show that Conjecture 2 is true within the class of hourglass-free graphs, i.e. graphs that do not contain an induced subgraph isomorphic to two triangles meeting in exactly one vertex. Next we show that a weaker form of Conjecture 2 is true, in which the conclusion is replaced by the conclusion that there exists a connected spanning subgraph in which each vertex has degree two or four. Finally we show that Conjecture 1 and 2 are equivalent to seemingly weaker conjectures in which the conclusion is replaced by the conclusion that there exists a spanning subgraph consisting of a bounded number of paths.
Original languageUndefined
Place of PublicationEnschede
PublisherUniversity of Twente
Number of pages13
ISBN (Print)0169-2690
Publication statusPublished - 1999

Publication series

NameMemorandum / Department of Applied Mathematics
PublisherDepartment of Applied Mathematics, University of Twente
ISSN (Print)0169-2690


  • MSC-05C38
  • MSC-05C45
  • IR-65680
  • METIS-141295
  • EWI-3311

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