SEMINAR: Groups and Combinatorics Seminar, Graphs are to matroids what ribbon graphs are to ...?
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Groups and Combinatorics Seminar, Graphs are to matroids what ribbon graphs are to ...? |
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Steven Noble (Brunel University)
will speak on
Graphs are to matroids what ribbon graphs are to ...?
at 3pm Friday April the 11th in Weatherburn Lecture Theatre.
Abstract:
Much of the combinatorial structure of an abstract connected graph is encoded in its set of spanning trees. These form one of the canonical examples of the bases of a matroid. Ribbon graphs contain extra topological information on the embedding of the underlying abstract graph in a surface. The structures playing the role of spanning trees are the subgraphs having one boundary component. The combinatorial structure which they form is a delta-matroid, which roughly speaking is like a matroid except that the bases do not need to have the same size. We will discuss three classes of delta-matroids, some natural operations on ribbon graphs which correspond to natural operations on delta-matroids, give an excluded minor theorem for one of the classes of delta-matroids and, time-permitting describe the Bollobas-Riordan polynomial which forms one way of generalizing the Tutte polynomial to ribbon graphs.
Speaker(s) |
Steven Noble (Brunel University)
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Location |
Weatherburn Lecture Theatre G.40
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Contact |
Irene Pivotto
<[email protected]>
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Start |
Fri, 11 Apr 2014 15:00
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End |
Fri, 11 Apr 2014 16:00
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Submitted by |
Irene Pivotto <[email protected]>
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Last Updated |
Wed, 09 Apr 2014 16:33
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