More powerful closure operations on graphs
β Scribed by Yong-jin Zhu; Feng Tian; Xiao-tie Deng
- Publisher
- Elsevier Science
- Year
- 1991
- Tongue
- English
- Weight
- 1017 KB
- Volume
- 87
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
β¦ Synopsis
Zhu, Y.-J., F. Tian and X.-T. Deng, More powerful closure operations on graphs, Discrete Mathematics 87 (1991) 197-214. Bondy and Chvatal have observed the following result: G = (V, E) is a simple graph of order n. If uu $ E and d(u) + d(u) 2 n, then G is Hamiltonian iff G + uu is Hamiltonian. Thus, we can obtain a graph C,(G), named the n-closure of G, from G by successively joining pairs of non-adjacent vertices whose degree sum is at least n. Therefore, G is Hamiltonian if C,(G) is Hamiltonian. Moreover, Bondy and Chvatal (21 generalized this idea to several properties on G. In the paper, we present some more powerful closure operations that extend the idea of Bondy and Chvatal.
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## Abstract A theorem of BirkhoffβFrink asserts that every algebraic closure operator on an ordinary set arises, from some algebraic structure on the set, as the corresponding generated subalgebra operator. However, for manyβsorted sets, i.e., indexed families of sets, such a theorem is not longer