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Is it true that every infinite finitely generated group contains an element of infinite period?

I think it is true, but I can't prove it.

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    Google "Tarski Monster" .2017-01-23
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    See the answer by "ndp" for a finitely generated counterexample at the duplicate.2018-02-13

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"This was once a paradox but now time gives it proof".

The simplest example is a consequence of the Golod-Shafarevitch theorem:

Theorem:For each prime $p$ there is an infinite group generated by three elements where each element has finite order a power of $p$.

See Herstein, Noncommutative Rings.

The proof of this is understandable and not too difficult. On the other hand there are a number of much more extreme examples (mostly with Russian names), whose proofs are just as monstrous, under the general heading of Burnside's Problem.

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The Grigorchuk group is finitely generated, and every element has finite order, but it is still infinite.