Combinatorica
Combinatorica
Topological paths, cycles and spanning trees in infinite graphs
European Journal of Combinatorics - Special issue: Topological graph theory
The Cycle Space of an Infinite Graph
Combinatorics, Probability and Computing
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Nash-Williams' arboricity theorem states that a finite graph is the edge-disjoint union of at most k forests if no set of @? vertices induces more than k(@?-1) edges. We prove a natural topological extension of this for locally finite infinite graphs, in which the partitioning forests are acyclic in the stronger sense that their Freudenthal compactification-the space obtained by adding their ends-contains no homeomorphic image of S^1. The strengthening we prove, which requires an upper bound on the end degrees of the graph, confirms a conjecture of Diestel [The cycle space of an infinite graph, Combin. Probab. Comput. 14 (2005) 59-79]. We further prove for locally finite graphs a topological version of the tree-packing theorem of Nash-Williams and Tutte.