Characterization of modular frobenius groups of special type

In this article, we first investigate the properties of modular Frobenius groups. Then, we consider the case that G' is a minimal normal subgroup of a modular Frobenius group G. We give the complete classification of G when G' as a modular Frobenius kernel has no more than four conjugacy classes in G.     

Length computation of matrix subalgebras of special type

Let {ie910-01} be a field and let {ie910-02} be a finite-dimensional {ie910-03}-algebra. We define the length of a finite generating set of this algebra as the smallest number k such that words of length not greater than k generate {ie910-04} as a vector space, and the length of the algebra is the maximum of the lengths of its generating sets. In this article, we give a series of examples of length computation for matrix subalgebras. In particular, we evaluate the lengths of certain upper triangular matrix subalgebras and their direct sums, and the lengths of classical commutative matrix subalgebras. The connection between the length of an algebra and the lengths of its subalgebras is also studied. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 13, No. 4, pp. 165–197, 2007.     

On a property of special groups

We show that Conjectures I and II of Serre about the vanishing ofH ¹ cannot be strengthened.Partially supported by NSF grant DMS-9801675.     

The chainable matrix,a special combinatorial matrix

The results of this paper comprise a study of a special class of combinatorial matrices called chainable matrices. The structure and algebraic behavior of these matrices are given specific attention.     

Rational permutation groups containing a full cycle

A finite group whose irreducible complex characters are rational valued is called a rational group. Thus, G is a rational group if and only if N _G (〈x〉)/C _G (〈x〉) ≌ Aut(〈x〉) for every x ∈ G. For example, all symmetric groups and their Sylow 2-subgroups are rational groups. Structure of rational groups have been studied extensively, but the general classification of rational groups has not been able to be done up to now. In this paper, we show that a full symmetric group of prime degree does not have any rational transitive proper subgroup and that a rational doubly transitive permutation group containing a full cycle is the full symmetric group. We also obtain several results related to the study of rational groups.     

Rational matrix pseudodifferential operators

The skewfield $\mathcal{K }(\partial )$ of rational pseudodifferential operators over a differential field $\mathcal{K }$ is the skewfield of fractions of the algebra of differential operators $\mathcal{K }[\partial ]$ . In our previous paper, we showed that any $H\in \mathcal{K }(\partial )$ has a minimal fractional decomposition $H=AB^{-1}$ , where $A,B\in \mathcal{K }[\partial ],\,B\ne 0$ , and any common right divisor of $A$ and $B$ is a non-zero element of $\mathcal{K }$ . Moreover, any right fractional decomposition of $H$ is obtained by multiplying $A$ and $B$ on the right by the same non-zero element of $\mathcal{K }[\partial ]$ . In the present paper, we study the ring $M_n(\mathcal{K }(\partial ))$ of $n\times n$ matrices over the skewfield $\mathcal{K }(\partial )$ . We show that similarly, any $H\in M_n(\mathcal{K }(\partial ))$ has a minimal fractional decomposition $H=AB^{-1}$ , where $A,B\in M_n(\mathcal{K }[\partial ]),\,B$ is non-degenerate, and any common right divisor of $A$ and $B$ is an invertible element of the ring $M_n(\mathcal{K }[\partial ])$ . Moreover, any right fractional decomposition of $H$ is obtained by multiplying $A$ and $B$ on the right by the same non-degenerate element of $M_n(\mathcal{K } [\partial ])$ . We give several equivalent definitions of the minimal fractional decomposition. These results are applied to the study of maximal isotropicity property, used in the theory of Dirac structures.     

The cohomology groups of a special Einstein manifold

Summary We consider a compact orientable Einstein manifold of even dimension n=2m, which is k-pinched. If k>[m(m−1) ₂ (2m−1) ₂ (2m−1)+3], then there exists no element, different from zero of the H ₂ (M,R) such that its exterior m-power belongs to a zero class. This result has some applications to the topological product of manifold. Entrata in Redazione il 27 settembre 1977.     

Bounded matrix groups

The principal result is that if G is any irreducible subgroup of GL(n, C) (C the complex field) such that |tr(7^)| is uniformly bounded for all A in G and some fixed n × n nonzero matrix T, then G is equivalent to a unitary group. Similar results are proved for certain associated representations of G.     

Tropical matrix groups

We study the structure of groups of finitary tropical matrices under multiplication. We show that the maximal groups of \(n \times n\) tropical matrices are precisely the groups of the form \(G \times \mathbb {R}\) where G is a group admitting a 2-closed permutation representation on n points. Each such maximal group is also naturally isomorphic to the full linear automorphism group of a related tropical polytope. Our results have numerous corollaries, including the fact that every automorphism of a projective (as a module) tropical polytope of full rank extends to an automorphism of the containing space.     

Bounded matrix groups

The principal result is that if G is any irreducible subgroup of GL(n, C) (C the complex field) such that |tr(7^)| is uniformly bounded for all A in G and some fixed n × n nonzero matrix T, then G is equivalent to a unitary group. Similar results are proved for certain associated representations of G.     

Studies in the matrix representability of abstract groups and in matrix groups

The author presents a summary of his dissertation in competition for the academic degree Doctor of Physicomathematical Sciences. The dissertation was defended on April 26, 1972, before the Academic Council of the Institute of Mathematics, Siberian Branch, Academy of Sciences of the USSR. The official opponents were Prof. D. M. Smirnov (Doctor of Physicomathematical Sciences), Prof. A. I. Starostin (Doctor of Physicomathematical Sciences of the Belorussian SSR and Doctor of Physicomathematical Sciences), and Prof. A. I. Shirshov (Corresponding Member of the Academy of Sciences of the USSR and Doctor of Physicomathematical Sciences).Translated from Matematicheskie Zametki, Vol. 14, No. 4, pp. 597–606, October, 1973.     

On finite groups admitting a special noncoprime action

An important result of Turull (1984) is the following:

Let be a finite solvable group, and . Then , where denotes the Fitting height and denotes the composition length.

The purpose of this work is to give a treatment of the minimal configuration in this framework with additional conditions, yet without the coprimeness condition.

     

Reduction of matrix polynomials to a special quasitriangular form

We find necessary and sufficient conditions for polynomials with matrix coefficients over an arbitrary field to be reducible via a similarity transformation to block triangular form with regular diagonal blocks of maximum degree. Translated fromMatematichni Metody i Fiziko-Mekhanichni Polya, Vol. 38, 1995.