On the heights of power digraphs modulo \(n\). (English) Zbl 1265.05274

To each pair of positive integers \(k\geq 2\) and \(n\) a digraph \(G(n,k)\) is assigned whose set of vertices is \(\{0,1,\dots ,n-1\}\) and \(\{(a,b)\: a^k\equiv b\pmod n\}\) is the set of its directed edges. The authors define the height of each vertex \(a\) as the shortest distance to the unique cycle of the component of \(G(n,k)\) that contains \(a\). They establish necessary and sufficient conditions on \(n\) such that each vertex of indegree 0 of a certain subdigraph of \(G(n,k)\) is at height \(q\geq 1\).
Reviewer: Michal Krizek


05C20 Directed graphs (digraphs), tournaments
11A07 Congruences; primitive roots; residue systems
11A15 Power residues, reciprocity
20K01 Finite abelian groups


Graphviz; Matlab
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