Nowhere-zero 3-flows and modulo k-orientations
نویسندگان
چکیده
منابع مشابه
Nowhere-zero 3-flows and modulo k-orientations
Article history: Received 30 October 2011 Available online 20 August 2013
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Let H be a connected graph and G be a supergraph of H . It is trivial that for any k-flow (D, f ) of G, the restriction of (D, f ) on the edge subset E(G/H) is a k-flow of the contracted graph G/H . However, the other direction of the question is neither trivial nor straightforward at all: for any k-flow (D′, f ′) of the contracted graph G/H , whether or not the supergraph G admits a k-flow (D,...
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Let G be a 2-edge-connected graph with o vertices of odd degree. It is well-known that one should (and can) add o 2 edges to G in order to obtain a graph which admits a nowhere-zero 2-flow. We prove that one can add to G a set of ≤ b o 4c, d2b o 5ce, and d2b o 7ce edges such that the resulting graph admits a nowhere-zero 3-flow, 4-flow, and 5-flow, respectively.
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Tutte observed that every nowhere-zero k-flow on a plane graph gives rise to a kvertex-coloring of its dual, and vice versa. Thus nowhere-zero integer flow and graph coloring can be viewed as dual concepts. Jaeger further shows that if a graph G has a face-k-colorable 2-cell embedding in some orientable surface, then it has a nowhere-zero k-flow. However, if the surface is nonorientable, then a...
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ژورنال
عنوان ژورنال: Journal of Combinatorial Theory, Series B
سال: 2013
ISSN: 0095-8956
DOI: 10.1016/j.jctb.2013.06.003