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Published online by Cambridge University Press: 11 August 2025
In 1954, B. H. Neumann discovered that if $G$ is a group in which all conjugacy classes have finite cardinality at most
$m$, then the derived group
$G'$ is finite of
$m$-bounded order. In 2018, G. Dierings and P. Shumyatsky showed that if
$|x^G| \le m$ for any commutator
$x\in G$, then the second derived group
$G''$ is finite and has
$m$-bounded order. This paper deals with finite groups in which
$|x^G|\le m$ whenever
$x\in G$ is a commutator of prime power order. The main result is that
$G''$ has
$m$-bounded order.