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THE GENERATING GRAPH OF INFINITE ABELIAN GROUPS

Part of: Graph theory Representation theory of groups Abelian groups

Published online by Cambridge University Press:  29 January 2019

CRISTINA ACCIARRI Open the ORCID record for CRISTINA ACCIARRI [Opens in a new window]  and
ANDREA LUCCHINI Open the ORCID record for ANDREA LUCCHINI [Opens in a new window]
CRISTINA ACCIARRI
Affiliation:
Department of Mathematics, University of Brasilia, 70910-900 Brasília DF, Brazil email acciarricristina@yahoo.it
ANDREA LUCCHINI*
Affiliation:
Università degli Studi di Padova, Dipartimento di Matematica ‘Tullio Levi-Civita’, Via Trieste 63, 35121 Padova, Italy email lucchini@math.unipd.it
*
✉lucchini@math.unipd.it
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Abstract

For a group $G$, let $\unicode[STIX]{x1D6E4}(G)$ denote the graph defined on the elements of $G$ in such a way that two distinct vertices are connected by an edge if and only if they generate $G$. Let $\unicode[STIX]{x1D6E4}^{\ast }(G)$ be the subgraph of $\unicode[STIX]{x1D6E4}(G)$ that is induced by all the vertices of $\unicode[STIX]{x1D6E4}(G)$ that are not isolated. We prove that if $G$ is a 2-generated noncyclic abelian group, then $\unicode[STIX]{x1D6E4}^{\ast }(G)$ is connected. Moreover, $\text{diam}(\unicode[STIX]{x1D6E4}^{\ast }(G))=2$ if the torsion subgroup of $G$ is nontrivial and $\text{diam}(\unicode[STIX]{x1D6E4}^{\ast }(G))=\infty$ otherwise. If $F$ is the free group of rank 2, then $\unicode[STIX]{x1D6E4}^{\ast }(F)$ is connected and we deduce from $\text{diam}(\unicode[STIX]{x1D6E4}^{\ast }(\mathbb{Z}\times \mathbb{Z}))=\infty$ that $\text{diam}(\unicode[STIX]{x1D6E4}^{\ast }(F))=\infty$.

Keywords

abelian groupsgenerationgenerating graphfree groupsFibonacci numbers

MSC classification

Primary: 20D60: Arithmetic and combinatorial problems
Secondary: 05C25: Graphs and abstract algebra (groups, rings, fields, etc.) 20K15: Torsion-free groups, finite rank
Type
Research Article
Information
Bulletin of the Australian Mathematical Society , Volume 100 , Issue 1 , August 2019 , pp. 68 - 75
Copyright
© 2019 Australian Mathematical Publishing Association Inc. 

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Footnotes

Research partially supported by MIUR-Italy via PRIN ‘Group theory and applications’. The first author is also supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq-Brazil and FAPDF.

References

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