The paper by E. I. Khukhro and P. Shumyatsky, Almost Engel finite and profinite groups has been accepted for publication in the International Journal of Algebra and Computation, ISSN 0218-1967, see also arXiv:1512.06097.
Abstract: Let be an element of a group
. For a positive integer
, let
be the subgroup generated by all commutators
over
, where
is repeated
times. We prove that if
is a profinite group such that for every
there is
such that
is finite, then
has a finite normal subgroup
such that
is locally nilpotent. The proof uses the Wilson–Zelmanov theorem saying that Engel profinite groups are locally nilpotent. In the case of a finite group
, we prove that if, for some
,
for all
, then the order of the nilpotent residual
is bounded in terms of
.