The distinguishing number of complete bipartite and crown graphs
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866912841087320064 |
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| author | Chen, Lei Devillers, Alice Morgan, Luke Rober, Friedrich |
| author_facet | Chen, Lei Devillers, Alice Morgan, Luke Rober, Friedrich |
| contents | The distinguishing number of a permutation group $G\leqslant\Sym(Ω)$ is the minimum number of colours needed to colour $Ω$ in such a way that the only colour preserving element of $G$ is the identity. The distinguishing number of a graph is the distinguishing number of its automorphism group (as a permutation group on vertices). We determine the distinguishing number of the complete bipartite graphs $K_{n,n}$ and the crown graphs $K_{n,n}-nK_2$, as well as the distinguishing number of some `large' subgroups of their automorphism groups, that is, the subgroups that are vertex- and edge-transitive and such that the induced action on each bipart is $\Alt(n)$ or $\Sym(n)$. We show that, if $G$ is a `large' group of automorphisms of $K_{n,n}$, then $n-1\leqslant D(G) \leqslant n+1$. Similarly, if $G$ is a `large' group of automorphisms of a crown graph, then $\lceil \sqrt{n-1}\rceil \leqslant D(G)\leqslant \lfloor \sqrt{n}\rfloor+1$.
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\textit{Keywords:} complete bipartite graph; crown graph; distinguishing number; symmetric group; alternating group |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2601_15913 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The distinguishing number of complete bipartite and crown graphs Chen, Lei Devillers, Alice Morgan, Luke Rober, Friedrich Combinatorics The distinguishing number of a permutation group $G\leqslant\Sym(Ω)$ is the minimum number of colours needed to colour $Ω$ in such a way that the only colour preserving element of $G$ is the identity. The distinguishing number of a graph is the distinguishing number of its automorphism group (as a permutation group on vertices). We determine the distinguishing number of the complete bipartite graphs $K_{n,n}$ and the crown graphs $K_{n,n}-nK_2$, as well as the distinguishing number of some `large' subgroups of their automorphism groups, that is, the subgroups that are vertex- and edge-transitive and such that the induced action on each bipart is $\Alt(n)$ or $\Sym(n)$. We show that, if $G$ is a `large' group of automorphisms of $K_{n,n}$, then $n-1\leqslant D(G) \leqslant n+1$. Similarly, if $G$ is a `large' group of automorphisms of a crown graph, then $\lceil \sqrt{n-1}\rceil \leqslant D(G)\leqslant \lfloor \sqrt{n}\rfloor+1$. \smallskip \textit{Keywords:} complete bipartite graph; crown graph; distinguishing number; symmetric group; alternating group |
| title | The distinguishing number of complete bipartite and crown graphs |
| topic | Combinatorics |
| url | https://arxiv.org/abs/2601.15913 |