Prof. G. Spencer-Brown, London

Lecture
       Oesterreichische Studiengesellschaft fuer Kybernetik (OeSGK)
                      Schottengasse 3, A-1010 Wien
                       Tel.+43-1-53532810,5336112
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                                VORTRAG
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Prof.Dr.George SPENCER-BROWN
London


Uncolourable Trivalent Graphs
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Plenary Lecture at the
13th European Meeting on Cybernetics and Systems Research
(EMCSR'96)

A 3-graph is said to be uncolourable if its links cannot be completely 
coloured with just three colours so that similarly-coloured links do not 
meet at any node. It is considered trivial if it is less than five-
connected, or if it can obviously be factored so that one of the factors 
is a smaller nontrivial uncolourable graph.

Isaacs (Am Math Monthly, 73 (1975) 221-239) described an infinite class 
of nontrivial uncolourable 3-graphs but was unable to answer the question
whether it accounts for all such graphs. The present communication 
demonstrates a method of factorization that supplies an affirmative 
answer to this question.

Zeit: Mittwoch, 10.April 1996, 9:00 Uhr pktl.
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Ort:  Hoersaal 47 im Hauptgebaeude der Universitaet Wien,
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      Dr.Karl Lueger-Ring 1, 1010 Wien 1.