On Maps with a Single Zigzag
- Sóstenes Lins sostenes@dmat.ufpe.br
- Valdenberg Silva valden@infonet.com.br
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Abstract
If a graph GM is embedded into a closed surface S such that S\GM is a collection of disjoint open discs, then M = 3D(GM, S) is called a map. A zigzag in a map M is a closed path which alternates choosing, at each star of a vertex, the leftmost and the rightmost possibilities for its next edge. If a map has a single zigzag we show that the cyclic ordering of the edges along it induces linear transformations, Cp and Cp∼ whose images and kernels are respectively the cycle and bond spaces (over GF(2)) of GM and GD, where D= 3D(GD, S) is the dual map of M. We prove that Im(cp o cp∼) is the intersection of the cycle spaces of GM and GD, and that the dimension of this subspace is connectivity of S. Finally, if M has also a single face, this face induces a linear transformation cD which is invertible: we show that C-1D = 3Dcp∼.
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