A Degree Theorem for the Space of Ribbon Graphs

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This paper extends results of Hatcher and Vogtmann's work "Cerf Theory for Graphs" to ribbon graphs. Given an orientable, punctured and basepointed surface Sigma, we prove that the space of ribbon graphs that can be drawn in Sigma is filtered by simplicial complexes. The k-th simplicial complex is (k-1)-dimensional, (k-2)-connected and invariant under the action of the basepoint preserving mapping class group of Sigma.