A group in a group

1. In an Abelian group, a module, or more generally a one-based group H, the only definable groups are the obvious ones: if G is interpretable in H, then it has a definable subgroup of finite index which is definably isomorphic to a quotient A/B, where A and B are definable subgroups of a Cartesian power of H. 2. In such a group the introduction of those quotient groups weakly eliminates imaginary elements. More generally, for a stable theory the existence of canonical real bases for complete types implies the elimination of imaginary elements. 3. A group which is interpretable in a one-based structure is one-based. The property of being one-based is preserved by interpretation for theories of finite rank but not in general.Translated from French.Translated from Algebra i Logika, No. 3, pp. 368–378, May–June, 1990.     

The Valentiner group as Galois group

We obtain the complete set of solutions to the Galois embedding problem given by the Valentiner group as a triple cover of the alternating group .

     

The Sheffer group and the Riordan group

We define the Sheffer group of all Sheffer-type polynomials and prove the isomorphism between the Sheffer group and the Riordan group. An equivalence of the Riordan array pair and generalized Stirling number pair is also presented. Finally, we discuss a higher dimensional extension of Riordan array pairs.     

Integral group ring of Rudvalis simple group

Using the Luthar–Passi method, we investigate the classical Zassenhaus conjecture for the normalized unit group of the integral group ring of the Rudvalis sporadic simple group Ru . As a consequence, for this group we confirm the Kimmerle conjecture on prime graphs. Published in Ukrains’kyi Matematychnyi Zhurnal, Vol. 61, No. 1, pp. 3–13, January, 2009.     

Graded group schemes and graded group varieties

We define graded group schemes and graded group varieties and develop their theory. Graded group schemes are the graded analogue of a?ne group schemes and are in correspondence with graded Hopf algebras. Graded group varieties take the place of infinitesimal group schemes. We generalize the result that connected graded bialgebras are graded Hopf algebra to our setting and we describe the algebra structure of graded group varieties. We relate these new objects to the classical ones providing a new and broader framework for the study of graded Hopf algebras and a?ne group schemes.     

The equivariant Brauer group of a group

We consider the Brauer group of a group (finite or infinite) over a commutative ring with identity. A split exact sequence

is obtained. This generalizes the Fröhlich-Wall exact sequence from the case of a field to the case of a commutative ring, and generalizes the Picco-Platzeck exact sequence from the finite case of to the infinite case of . Here is the Brauer-Taylor group of Azumaya algebras (not necessarily with unit). The method developed in this paper might provide a key to computing the equivariant Brauer group of an infinite quantum group.

     

finite groups with schmidt group as automorphism group

This paper continues the work of D.MacHale,D.Flannery(Proc.R.Ir.Acad.81A,209—215;83A,189—196)and the author(Proc.R.Ir.Acad,90A,57—62;J.Southwest China Normal University 15,No.1,21.—28)on the topic on“Finite groupswith given Automorphism group”.The following result is proved:Let G be a finite group with Aut G a Schmidt group.Then G is isomorphic toS_3 or Klain 4-group.,or D such that Aut D=Inn D.D is aSchmidt group of order 2~(?)p.S_2(∈Syl_2D)is a normal and special group exoept asupersperspecial group without commutative generators.     

The permutation class group of a finite group

Analogously to the projective class group, the permutation class group of a finite group π can be defined as the group of equivalence classes of direct summands of integral permutation modules modulo permutation modules. It is shown that this group behaves nicely with respect to localization and completion, which then is used to prove that contrary to the projective class group - it is not always a torsion group. More precisely, the rank of the permutation class of group is computed.     

The group algebra of the infinite symmetric group

The rational group algebra of the infinite symmetric group is studied using Young diagrams. Maximal and prime ideals are characterized and the maximal condition on ideals is proved. Research supported by the National Research Council of Canada.     

The automorphism group of the augmented equiaffine group

The automorphism group of the group generated by all the affine reflections in a Desarguesian plane is isomorphic to the full collineation group of the plane.The author wishes to express his thanks to J. Wilker of the University of Toronto for suggesting a simplification and to him as well as C. Fisher of the University of Regina for their encouragement.     

Abelian group pairs having a trivial coGalois group

Torsion-free covers are considered for objects in the category q ₂. Objects in the category q ₂ are just maps in R-Mod. For R = ℤ, we find necessary and sufficient conditions for the coGalois group G(A → B), associated to a torsion-free cover, to be trivial for an object A → B in q ₂. Our results generalize those of E. Enochs and J. Rado for abelian groups.     

Modular group rings of the finitary symmetric group

The paper discusses approaches to constructing two-sided ideals of the modular group algebra of finitary symmetric group. In memory of Professor S. A. Amitsur