On sequences of word maps of compact topological groups
Zapiski Nauchnykh Seminarov POMI, Problems in the theory of representations of algebras and groups. Part 35, Tome 492 (2020), pp. 94-124 Cet article a éte moissonné depuis la source Math-Net.Ru

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In the paper of A. Thom (A. Thom, Convergent sequences in discrete groups, Canad. Math. Bull. 56 (2013), 424–433) it has been proved that for any standard unitary group $\mathrm{SU}(\mathbb{C})$ (the compact form) and for any real number $\epsilon > 0$ there is a non-trivial word $w(x, y)$ on two variables such that the image of the word map $\tilde{w}: \mathrm{SU}_n(\mathbb{C})^2\rightarrow \mathrm{SU}_n (\mathbb{C})$ is contained in $\epsilon$-neighbourhood of the identity of the group $\mathrm{SU}_n(\mathbb{C})$. Actually, in Thom's paper there is a construction of a sequence $\{w_j\}_{j \in \mathbb{N}}$, where $w_j \in F_2$, that converges uniformly on a compact group to the identity. In this paper we propose a method for the construction of such sequences. Also, using the result of T. Bandman, G-M. Greuel, F. Grunewald, B. Kunyavskii, G. Pfister and E. Plotkin, Identities for finite solvable groups and equations in finite simple groups. – Compositio Math. 142 (2006) 734-764), we construct the sequence of the surjective word maps $\tilde{w}_j: \mathrm{SU}_2(\mathbb{C})^n\rightarrow \mathrm{SU}_2(\mathbb{C})$, where each word $w_j$ is contained in the corresponding member $F_n^j$ of the derived series of the free group $F_n$. We also make some comments and remarks which are relevant to such results and to general properties of word maps of compact groups.
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N. L. Gordeev. On sequences of word maps of compact topological groups. Zapiski Nauchnykh Seminarov POMI, Problems in the theory of representations of algebras and groups. Part 35, Tome 492 (2020), pp. 94-124. http://geodesic.mathdoc.fr/item/ZNSL_2020_492_a7/

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