Let k be a positive integer, and D = (V (D), E(D)) be a minimally k-edge-connected simple digraph. We denote the outdegree and indegree of x ∈ V (D) by δ D (x) and ρ D (x), respectively. Let u + (D) denote the number of vertices W. Mader asked the following question in [Mader, in Paul Erdös is Eigh
On Vertices of outdegree n in minimally n-connected digraphs
✍ Scribed by W. Mader
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 202 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Let |D| and |D|^+^~n~ denote the number of vertices of D and the number of vertices of outdegree n in the digraph D, respectively. It is proved that every minimally n‐connected, finite digraph D has |D|^+^~n~ ≥ n + 1 and that for n ≥ 2, there is a c~n~ > 0 such that $|D|^+_n > C_n \sqrt{|D|}$ for all minimally n‐connected, finite digraphs D. Furthermore, case n = 2 of the following conjecture is settled which says that every minimally n‐connected, finite digraph has a vertex of indegree and outdegree equal to n. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 129–144, 2002
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