Extension conjecture for edge-disjoint branchings in digraphs

Let D=(V,A)D=(V,A) be a digraph, let κ\kappa be an infinite cardinal, and let Bi=(Vi,Ai)\mathcal{B}_i=(V_i,A_i) for i<κi<\kappa be edge-disjoint branchings in DD. Define

DB=(V,Ai<κAi).D\setminus\mathcal{B}=(V,A\setminus\bigcup_{i<\kappa}A_i).

Suppose that DBD\setminus\mathcal{B} contains no forward-infinite paths and that, for every vVv\in V, there is a system of edge-disjoint paths {Pi}i<κ\{P_i\}_{i<\kappa} in DBD\setminus\mathcal{B} such that PiP_i goes from ViV_i to vv. Branching extension conjecture. The branchings Bi\mathcal{B}_i can be extended, without changing their root sets, to edge-disjoint spanning branchings of DD. This is an extension problem for infinitely many edge-disjoint branchings under a no-forward-infinite-path condition; the supplied source does not provide evidence resolving the assertion.

Sources & referencesView supporting material

Primary source

Attila Joó, “Edmonds' Branching Theorem in Digraphs without Forward-infinite Paths”, arXiv:1705.00471 (2017).

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