A theorem of Myasnikov and Roman'kov says that any verbally closed subgroup
of a finitely generated free group is a retract. We prove that all free (and
many virtually free) verbally closed subgroups are retracts in any finitely
generated group.Comment: 5 pages. A Russian version of this paper is at
http://halgebra.math.msu.su/staff/klyachko/papers.htm . V.2: an example is
added. V.3: minor corrections in the proof of the Main Theorem. V.4:
terminology correctio
It was recently proven that all free and many virtually free verbally closed subgroups are algebraically closed in any group. We establish sufficient conditions for a group that is an extension of a free non-abelian group by a group satisfying a non-trivial law to be algebraically closed in any group in which it is verbally closed. We apply these conditions to prove that the fundamental groups of all closed surfaces, except the Klein bottle, and almost all free products of groups satisfying a non-trivial law are algebraically closed in any group in which they are verbally closed.
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