We provide upper estimates on the spectral radius of a directed graph. In particular w e prove that the spectral radius is bounded by the maximum of the geometric mean of in-degree and out-degree taken over all vertices.
Iterating the branching operation on a directed graph
โ Scribed by Athanasiadis, Christos A.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 118 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
โฆ Synopsis
The branching operation D, defined by Propp, assigns to any directed graph G another directed graph D(G) whose vertices are the oriented rooted spanning trees of the original graph G. We characterize the directed graphs G for which the sequence ฮด(G) = (G, D(G), D 2 (G), . . .) converges, meaning that it is eventually constant. As a corollary of the proof we get the following conjecture of Propp: for strongly connected directed graphs G, ฮด(G) converges if and only if D 2 (G) = D(G).
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