| On Leighton's graph covering theorem (2009) | |||||||||
Abstract | |||||||||
| We give short expositions of both Leighton's proof and the Bass-Kulkarni proof of Leighton's graph covering theorem, in the context of colored graphs. We discuss a further generalization, needed elsewhere, to ``symmetry-restricted graphs.'' We can prove it in some cases, for example, if the ``graph of colors'' is a tree, but we do not know if it is true in general. We show that Bass's Conjugation Theorem, which is a tool in the Bass-Kulkarni approach, does hold in the symmetry-restricted context.. Comment: & pages, 2 figs | |||||||||
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