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EnglishA mixed hypergraph is characterized by the fact that it possesses C-edges as well as D-edges. In a colouring of a mixed hypergraph, every C-edge has at least two vertices of the same colour and every D-edge has at least two vertices coloured differently. The upper and lower chromatic numbers \bar(\chi), \chi are the maximum and minimum numbers of colours for which there exists a colouring using all the colours. The concepts of mixed hypergraph, upper and lower chromatic numbers are applied to SQSs. In fact a BSQS is an SQS where all the blocks are at the same time C-edges and D-edges. In this paper we prove that any BSQS(16) is colourable with the upper chromatic number \bar(\chi) = 3 and we give new information about the chromatic spectrum of BSQSs(16).
| Titolo: | On the upper and lower chromatic numbers of BSQS(16) |
| Autori interni: | |
| Data di pubblicazione: | 2001 |
| Rivista: | |
| Handle: | http://hdl.handle.net/20.500.11769/21303 |
| Appare nelle tipologie: | 1.1 Articolo in rivista |
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