Thompson's group $F$ is almost $\frac{3}{2}$-generated
Recall that a group $G$ is said to be $\frac{3}{2}$-generated if every non-trivial element of $G$ belongs to a generating pair of $G$. Thompson's group $V$ was proved to be $\frac{3}{2}$-generated by Donoven and Harper in 2019. It was the first example of an infinite finitely presented non-cycl...
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Zusammenfassung: | Recall that a group $G$ is said to be $\frac{3}{2}$-generated if every
non-trivial element of $G$ belongs to a generating pair of $G$. Thompson's
group $V$ was proved to be $\frac{3}{2}$-generated by Donoven and Harper in
2019. It was the first example of an infinite finitely presented non-cyclic
$\frac{3}{2}$-generated group. Recently, Bleak, Harper and Skipper proved that
Thompson's group $T$ is also $\frac{3}{2}$-generated. In this paper, we prove
that Thompson's group $F$ is "almost" $\frac{3}{2}$-generated in the sense that
every element of $F$ whose image in the abelianization forms part of a
generating pair of $\mathbb{Z}^2$ is part of a generating pair of $F$. We also
prove that for every non-trivial element $f\in F$ there is an element $g\in F$
such that the subgroup $\langle f,g\rangle$ contains the derived subgroup of
$F$. Moreover, if $f$ does not belong to the derived subgroup of $F$, then
there is an element $g\in F$ such that $\langle f,g\rangle$ has finite index in
$F$. |
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DOI: | 10.48550/arxiv.2210.03564 |