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Large scale properties of groups; growth functions; Dehn functions; small cancellation properties; hyperbolicity and CAT(0); actions and representations; combinatorial group theory; presentations

6 votes

Group of exponential growth always contains a free sub-group?

Not necessarily. -- For example, the lamplighter group has exponential growth, but does not have a free subgroup of rank 2 (if $a$ and $b$ are two elements of that group of infinite order, then there …
Stefan Kohl's user avatar
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10 votes
Accepted

Is it true that every f.g. infinite simple group has exponential growth?

No, there exists a finitely generated infinite simple group of intermediate growth. This has meanwhile been found out by Volodymyr Nekrashevych, cf. Palindromic subshifts and simple periodic groups o …
Stefan Kohl's user avatar
  • 19.6k
3 votes

Is there a highly transitive action of a finitely generated torsion simple group?

As you expressed interest in Thompson's group V in the comments -- the following is a highly transitive faithful permutation representation of V on $\mathbb{Z}$ (although as Ives de Cornulier has alre …
Stefan Kohl's user avatar
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16 votes
1 answer
913 views

Is it true that every f.g. infinite simple group has exponential growth?

Is it true that every finitely generated infinite simple group has exponential (word-)growth? Remark: As Mark Sapir has pointed out, the question whether every finitely generated group of subexponent …
Stefan Kohl's user avatar
  • 19.6k
3 votes

Proving that a countable group is not finitely generated

One possible way of proving that a countable group $G$ is not finitely generated is finding an infinite set $S$ and a mapping $\varphi$ from $G$ to the power set of $S$ such that the following hold: …
Stefan Kohl's user avatar
  • 19.6k