Intervenant:
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 Feliu Sagols, Département de Mathématiques, CINVESTAV, Mexico

Titre : Reducibility of three terminal planar graphs
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Résumé :	
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In 1966, G. Epifanov proved the Akers-Lehman conjecture, that any planar
graph with two terminals can be reduced by means of DELTA-WYE
transformations to a single edge, the last two nodes being the original
two terminals. In 1991, I. Gitler proved the three terminal planar
conjecture. We give a new proof of the 3-terminal case using these
operations on the medial graph, by proving that any planar graph with
three terminals can be reduced to one of the following graphs:

1. A path of length three
2. A path of length three v0, v1, v2 plus the loop (v1,v1), embedded in
such a way that exactly one of the edges (v0,v1) or (v1,v2) is in the
interior of the loop.