
arXiv: 1608.03501
The distinguishing number (index) $D(G)$ ($D'(G)$) of a graph $G$ is the least integer $d$ such that $G$ has an vertex (edge) labeling with $d$ labels that is preserved only by the trivial automorphism. It is known that for every graph $G$ we have $D'(G) \leq D(G) + 1$. In this note we characterize trees for which this inequality is sharp. We also show that if $G$ is a connected unicyclic graph, then $D'(G) = D(G)$.
9 pages
automorphism group, tree, Trees, 05C15, 05E18, Group actions on combinatorial structures, 05e18, Coloring of graphs and hypergraphs, distinguishing index, 05c15, QA1-939, FOS: Mathematics, Mathematics - Combinatorics, Combinatorics (math.CO), unicyclic graph, Mathematics, distinguishing number
automorphism group, tree, Trees, 05C15, 05E18, Group actions on combinatorial structures, 05e18, Coloring of graphs and hypergraphs, distinguishing index, 05c15, QA1-939, FOS: Mathematics, Mathematics - Combinatorics, Combinatorics (math.CO), unicyclic graph, Mathematics, distinguishing number
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