S-functions for graphs
- Cite this article as:
- Halin, R. J Geom (1976) 8: 171. doi:10.1007/BF01917434
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S-functions are mappings from the class of finite graphs into the set of integers, such that certain formal conditions are fulfilled which are shared by the chromatic number, the vertex-connectivity, and the homomorphism-degree. The S-functions form a complete lattice (with respect to their natural partial order). The classes of graphs with values <n under some S-function are studied from a general point of view, and uncountably many S-functions are constructed. Further for every n≥5 a non-trivial base-element of (see K. WAGNER ) is constructed.
© Birkhäuser Verlag 1976