Abstract
A digraph D of order n is r-hypohamiltonian (respectively r-hypotraceable) for some positive integer r < n − 1 if D is nonhamiltonian (nontraceable) and the deletion of any r of its vertices leaves a hamiltonian (traceable) digraph. A 1-hypohamiltonian (1-traceable) digraph is simply called hypohamiltonian (hypotraceable). Although hypohamiltonian and hypotraceable digraphs are well-known and well-studied concepts, we have found no mention of r-hypohamiltonian or r-hypotraceable digraphs in the literature for any r > 1. In this paper we present infinitely many 2-hypohamiltonian oriented graphs and use these to construct infinitely many 2-hypotraceable oriented graphs. We also discuss an interesting connection between the existence of r-hypotraceable oriented graphs and the Path Partition Conjecture for oriented graphs.
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This material is based upon work supported by the National Research Foundation of South Africa under Grant numbers 77248 and 71308.
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van Aardt, S.A., Burger, A.P., Frick, M. et al. Infinite families of 2-hypohamiltonian/2-hypotraceable oriented graphs. Graphs and Combinatorics 30, 783–800 (2014). https://doi.org/10.1007/s00373-013-1312-1
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DOI: https://doi.org/10.1007/s00373-013-1312-1
Keywords
- hypohamiltonian
- 2-hypohamiltonian
- hypo-hypohamiltonian
- hypotraceable
- 2-hypotraceable
- hypo-hypotraceable
- Traceability Conjecture
- Path Partition Conjecture