Let $q$ be a prime and let $A$ be an elementary abelian group of order at least $q^{3}$ acting by automorphisms on a finite $q^{\prime }$-group $G$. We prove that if $|\unicode[STIX]{x1D6FE}_{\infty }(C_{G}(a))|\leq m$ for any $a\in A^{\#}$, then the order of $\unicode[STIX]{x1D6FE}_{\infty }(G)$ is $m$-bounded. If $F(C_{G}(a))$ has index at most $m$ in $C_{G}(a)$ for any $a\in A^{\#}$, then the index of $F_{2}(G)$ is $m$-bounded.
Abstract
Let q be a prime and A a finite q-group of exponent q acting by automorphisms on a finite
{q^{\prime}}
-group G.
Assume that A has order at least
{q^{3}}
.
We show that if
{\gamma_{\infty}(C_{G}(a))}
has order at most m for any
{a\in A^{\#}}
, then the order of
{\gamma_{\infty}(G)}
is bounded solely in terms of m.
If the Fitting subgroup of
{C_{G}(a)}
has index at most m for any
{a\in A^{\#}}
, then the second Fitting subgroup of G has index bounded solely in terms of m.