Frobenius action on Carter subgroups

Abstract: Let $G$ be a finite solvable group and $H$ be a subgroup of $Aut(G)$. Suppose that there exists an $H$-invariant Carter subgroup $F$ of $G$ such that the semidirect product $FH$ is a Frobenius group with kernel $F$. We prove that the terms of the Fitting series of $C_{G}(H)$ are obtained as the intersection of $C_{G}(H)$ with the corresponding terms of the Fitting series of $G$, and the Fitting height of $G$ may exceed the Fitting height of $C_{G}(H)$ by at most one. As a corollary it is shown that for any set of primes $\pi$, the terms of the $\pi$-series of $C_{G}(H)$ is obtained as the intersection of $C_{G}(H)$ with the corresponding terms of the $\pi$-series of $G$, and the $\pi$-length of $G$ may exceed the $\pi$-length of $C_{G}(H)$ by at most one. They generalize the main results of \cite{Khu}.