The mean chromatic number of a graph is a measure of the expected performance of the greedy vertex-colouring algorithm when each ordering of the vertices is equally likely. Some results on the value of the mean chromatic number and its asymptotic behaviour are presented.
On the finiteness of the recursive chromatic number
β Scribed by William I. Gasarch; Andrew C.Y. Lee
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 559 KB
- Volume
- 93
- Category
- Article
- ISSN
- 0168-0072
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β¦ Synopsis
A recursive graph is a graph whose vertex and edge sets are recursive.
A highly recursive graph is a recursive graph that also has the following property: one can recursively determine the neighbors of a vertex. Both of these have been studied in the literature. We consider an intermediary notion: Let A be a set. An A-recursive graph is a recursive graph that also has the following property: one can recursively-in-A determine the neighbors of a vertex. We show that, if A is r.e. and not recursive, then there exists A-recursive graphs that are 2-colorable but not recursively k-colorable for any k. This is false for highly-recursive graphs but true for recursive graphs. Hence A-recursive graphs are closer in spirit to recursive graphs than to highly recursive graphs.
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