Abstract
The classic Magnus embedding is a very effective tool in the study of abelian extensions of a finitely generated group \(G\), allowing us to see the extension as a subgroup of a wreath product of a free abelian group with \(G\). In particular, the embedding has proved to be useful when studying free solvable groups. An equivalent geometric definition of the Magnus embedding is constructed and it is used to show that it is \(2\)-bi-Lipschitz, with respect to an obvious choice of generating sets. This is then applied to obtain a non-zero lower bound on \(L_p\) compression exponents in free solvable groups.
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Acknowledgments
The author would like to thank Cornelia Druţu for many valuable discussions on this paper. Alexander Olshanskii’s comments on a draft copy were also very helpful, as were discussions with Romain Tessera. He would also like to thank David Hume for useful discussions on \(L^p\) compression exponents.
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The author was supported by the EPSRC.
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Sale, A.W. Metric behaviour of the Magnus embedding. Geom Dedicata 176, 305–313 (2015). https://doi.org/10.1007/s10711-014-9969-z
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DOI: https://doi.org/10.1007/s10711-014-9969-z