Holonomy groups of Bieberbach groups with finite outer automorphism groups

This work was supported by the DFG and by a Polish grant BW/5100-5-0116-3.     

On automorphism groups of some finite groups

We show that if n > 1 is odd and has no divisor p4 for any prime p, then there is no finite group G such that│Aut(G)│ = n.     

Kazhdan groups with infinite outer automorphism group

For each countable group we produce a short exact sequence where has a graphical presentation and is f.g. and satisfies property .

As a consequence we produce a group with property  such that is infinite.

Using the tools developed we are also able to produce examples of non-Hopfian and non-coHopfian groups with property .

One of our main tools is the use of random groups to achieve certain properties.

     

On coleman outer automorphism groups of finite groups

Let G be a finite group and Out _Col(G) the Coleman outer automorphism group of G(for the definition, see below). The question whether Out_Col(G) is a p′-group naturally arises from the study of the normalizer problem for integral group rings, where p is a prime. In this article, some sufficient conditions for Out_Col(G) to be a p′-group are obtained. Our results generalize some well-known theorems.     

Quantum automorphism groups of finite graphs

A quantum analogue of the automorphism group of a finite graph is introduced. These are quantum subgroups of the quantum permutation groups defined by Wang. The quantum automorphism group is a stronger invariant for finite graphs than the usual automorphism group. We get a quantum dihedral group .

     

Regular representations of finite groups as automorphism groups of k‐tournaments

It was shown by Babai and Imrich [2] that every finite group of odd order except and admits a regular representation as the automorphism group of a tournament. Here, we show that for k ≥ 3, every finite group whose order is relatively prime to and strictly larger than k admits a regular representation as the automorphism group of a k‐tournament. Our constructions are elementary, suggesting that the problem is significantly simpler for k‐tournaments than for binary tournaments. © 2002 Wiley Periodicals, Inc. J Graph Theory 41: 238–248, 2002     

Minimal non-nilpotent groups as automorphism groups

Groups are classified whose automorphism group is minimal non-nilpotent.The first author wishes to thank the Mathematics Department of Napoli for its warm hospitality for the time of writing this paper.     

Infinite locally dihedral groups as automorphism groups

If \(A\) is a nontrivial torsion-free, locally cyclic group with no nontrivial divisible quotients, and \(G\) is the split extension of \(A\) by a group of order 2 acting on \(A\) by means of the inverting map, then \(G\simeq {{{\mathrm{Aut}}}G} \). We prove that in no other case the full automorphism group of a group is infinite and locally dihedral.     

Solvable line-transitive automorphism groups of finite linear spaces

Let S be a finite linear space, and letG be a group of automorphisms of S. IfG is soluble and line-transitive, then for a givenk but a finite number of pairs of (S, G),S hasv= p ⁿ points andG ⩽AΓL(1,p ⁿ ).