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Let A be a finite nilpotent group acting fixed point freely on the finite (solvable) group G by automorphisms. It is conjectured that the nilpotent length of G is bounded above by ℓ (A) , the number of primes dividing the order of A counted with multiplicities. In the present paper we consider the case A is cyclic and obtain that the nilpotent length of G is at most 2 ℓ (A) if | G | is odd. More generally we prove that the nilpotent length of G is at most 2 ℓ (A) + c (G ; A) when G is of odd order and A normalizes a Sylow system of G where c (G ; A) denotes the number of trivial A -modules appearing in an A -composition series of G. [ABSTRACT FROM AUTHOR]

Let G and A be finite groups with A acting on G by automorphisms. In this paper we introduce the concept of "good action"; namely we say the action of A on G is good, if H = H , B C H (B) for every subgroup B of A and every B -invariant subgroup H of G. This definition allows us to prove a new noncoprime Hall-Higman type theorem. If A is a nilpotent group acting on the finite solvable group G with C G (A) = 1 , a long standing conjecture states that h (G) ⩽ ℓ (A) where h (G) is the Fitting height of G and ℓ (A) is the number of primes dividing the order of A counted with multiplicities. As an application of our result we prove the main theorem of this paper which states that the above conjecture is true if A and G have odd order, the action of A on G is good and some other fairly general conditions are satisfied. [ABSTRACT FROM AUTHOR]

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 F H is a Frobenius group with kernel F and complement H. 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 π , the terms of the π -series of C G (H) are obtained as the intersection of C G (H) with the corresponding terms of the π -series of G , and the π -length of G may exceed the π -length of C G (H) by at most one. These theorems generalize the main results in [E. I. Khukhro, Fitting height of a finite group with a Frobenius group of automorphisms, J. Algebra366 (2012) 1–11] obtained by Khukhro. [ABSTRACT FROM AUTHOR]

A subgroup H of a group G is said to be a TNI-subgroup if for any Let A be an abelian group acting coprimely on the finite group G by automorphisms in such a way that for all is a solvable TNI-subgroup of G. We prove that G is a solvable group with Fitting length h(G) is at most. In particular whenever is nonnormal. Here, h(G) is the Fitting length of G and is the number of primes dividing A counted with multiplicities. [ABSTRACT FROM AUTHOR]

Abstract Let FH be a Frobenius group with kernel F and complement H , acting coprimely on the finite solvable group G by automorphisms. We prove that if C G (H) is of Fitting length n then the index of the n -th Fitting subgroup F n (G) in G is bounded in terms of | C G (F) | and | F |. This generalizes a result of Khukhro and Makarenko [6] which handles the case n = 1. [ABSTRACT FROM AUTHOR]

In this study we have obtained some sufficient conditions for the Taketa inequality namely dl(G) ≤ |cd(G)| for finite solvable groups G. [ABSTRACT FROM AUTHOR]

Let G be a finite group and α be an automorphism of G of order pn for an odd prime p. Suppose that α acts fixed point freely on every α-invariant p′-section of G, and acts trivially or exceptionally on every elementary abelian α-invariant p-section of G. It is proved that G is a solvable p-nilpotent group of nilpotent length at most n + 1, and this bound is best possible. [ABSTRACT FROM AUTHOR]

Let A be a finite group acting fixed-point freely on a finite (solvable) group G. A longstanding conjecture is that if (|G|, |A|) = 1, then the Fitting length of G is bounded by the length of the longest chain of subgroups of A. It is expected that the conjecture is true when the coprimeness condition is replaced by the assumption that A is nilpotent. We establish the conjecture without the coprimeness condition in the case where A is an abelian group whose order is a product of three odd primes and where the Sylow 2-subgroups of G are abelian. [ABSTRACT FROM AUTHOR]

Abstract: Let A be a finite abelian group that acts fixed point freely on a finite (solvable) group G. Assume that is odd and A is of squarefree exponent coprime to 6. We show that the Fitting length of G is bounded by the length of the longest chain of subgroups of A. [Copyright &y& Elsevier]