Let T be a (first order complete) dependent theory, C a κ̄-saturated model of T and G a definable subgroup which is abelian. Among subgroups of bounded index which are the union of < κ̄ type definable subsets there is a minimal one, i.e. their intersection has bounded index. See history in [Sh:876]. We then deal with definable groups for 2-dependent theories, a wider class of first order theories...

We show that the order complex of the subgroup lattice of a finite group G is nonpure shellable if and only if G is solvable. A by-product of the proof that nonsolvable groups do not have shellable subgroup lattices is the determination of the homotopy types of the order complexes of the subgroup lattices of many minimal simple groups.

There is a longstanding conjecture, due to Gregory Cherlin and Boris Zilber, that all simple groups of finite Morley rank are simple algebraic groups. One of the major theorems in the area is Borovik’s trichotomy theorem. The ‘trichotomy’ here is a case division of the generic minimal counterexamples within odd type, that is, groups with a large and divisible Sylow◦ 2-subgroup. The so-called ‘u...

In this paper, we describe the theory and implementation of algorithms for computing chief series, composition series and socles in large permutation groups. The theory is valid for permutation degrees up to 10 000 000. Most parts of the algorithms have been implemented within the Magma Computational Algebra System (Bosma and Cannon, 1993; Bosma et al., 1994; Bosma et al., 1997; Cannon and Play...

Let G be a finite group, and let F be a formation of finite group. We say that a subgroup H of G is p F -normal in G if there exists a normal subgroup T of G such that HT is a permutable Hall subgroup of G and G G H H T H / ) ( is contained in the F-hypercenter ) / ( G F H G Z of G H G / . In this note, we get some results about the p F -normal subgroups and then use them to study the structure...

A permutation group is innately transitive if it has a transitive minimal normal subgroup, and this subgroup is called a plinth. In this paper we study three special types of inclusions of innately transitive permutation groups in wreath products in product action. This is achieved by studying the natural Cartesian decomposition of the underlying set that correspond to the product action of a w...

The aim of this note is to determine whether certain non-o-minimal expansions of o-minimal theories which are known to be NIP, are also distal. We observe that while tame pairs of o-minimal structures and the real field with a discrete multiplicative subgroup have distal theories, dense pairs of o-minimal structures and related examples do not.

A transitively normal subgroup of a group G is one that is normal in every subgroup in which it is subnormal. This concept is obviously related to the transitivity of normality because the latter holds in every subgroup of a group G if and only if every subgroup of G is transitively normal. In this paper we describe the structure of a group whose cyclic subgroups (or a part of them) are transit...