Enlarging vertex-flames in countable digraphs

Joshua Erde*, J. Pascal Gollin, Attila Joó

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A rooted digraph is a vertex-flame if for every vertex v there is a set of internally disjoint directed paths from the root to v whose set of terminal edges covers all ingoing edges of v. It was shown by Lovász that every finite rooted digraph admits a spanning subdigraph which is a vertex-flame and large, where the latter means that it preserves the local connectivity to each vertex from the root. Calvillo-Vives rediscovered and extended this theorem proving that every vertex-flame of a given finite rooted digraph can be extended to be large. The analogue of Lovász' result for countable digraphs was shown by the third author where the notion of largeness is interpreted in a structural way as in the infinite version of Menger's theorem. We give a common generalisation of this and Calvillo-Vives' result by showing that in every countable rooted digraph each vertex-flame can be extended to a large vertex-flame.

Original languageEnglish
Pages (from-to)263-281
Number of pages19
JournalJournal of Combinatorial Theory, Series B
Publication statusPublished - Nov 2021


  • Infinite graphs
  • Flames
  • Infinite digraph
  • Local connectivity
  • Flame

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Discrete Mathematics and Combinatorics
  • Computational Theory and Mathematics


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