Irreducible subgroups of SL(n,K) generated by root subgroups

Jack McLaughlin determines all the irreducible subgroups of SL(n, K) generated by root subgroups for commutative fields K. In this paper I do the same thing for noncommutative division rings K.     

The variety of pairs of commuting nilpotent matrices is irreducible

In this paper we prove the dimension and the irreduciblity of the variety parametrizing all pairs of commuting nilpotent matrices. Our proof uses the connection between this variety and the punctual Hilbert scheme of a smooth algebraic surface.     

Invariants of linear groups generated by matrices with two nonunit eigenvalues

A theorem on the structure of the algebra of invariants of the commutant of a group generated by pseudoreflections is improved. In particular, it is shown that this algebra is a complete intersection. A series of counterexamples to Stanley's conjecture is constructed in dimension 4. Results supporting this conjecture for primitive groups of large dimension are given.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 114, pp. 120–130, 1982.     

Irreducible matrices with reducible principal submatrices

Let A be a (0, 1)-matrix of order n 3 and let s_i⁰(A), i = 1, …, n, be the number of the off diagonal 0's in row and column i of A. We prove that if A is irreducible, and if all its principal submatrices of order (n − 1) are reducible, then s_i⁰(A) n − 1; i = 1, …, n. This establishes the validity of a conjecture by B. Schwarz concerning strongly connected graphs and their primal subgraphs.     

Products of irreducible matrices

In this paper we characterize the subsemigroup of B_n (B_n is the multiplicative semigroup of n × n Boolean matrices) generated by all the irreducible matrices, and hence give a necessary and sufficient condition for a Boolean matrix A to be a product of irreducible Boolean matrices. We also give a necessary and sufficient condition for an n × n nonnegative matrix to be a product of nonnegative irreducible matrices.     

Quotient finite dimensional modules with acc on subdirectly irreducible submodules are noetherian

A right R-module M is (Goldie) finite dimensional (= f.d.) if M contains no infinite direct sums of submodules.M is quotient f.d. (= q.f.d.) if M/K is f.d. for all submodules K.A submodule I of M is subdirectly irreducible (= SDI) if V is the intersection of all submodules S _α of M that properly contain I, then V ≠ I, equivalentlyM/I has simple essential socle V/I. A theorem of Shock [74] states that a q.f.d. right module M is Noether-ian iff every proper submodule of M is contained in a maximal submodule. Camillo [77], proved a companion theorem: M is q.f.d. iff every submodule A ≠ 0 contains a finitely generated (= f.g) submodule S such that A/S has no maximal submodules. Using these two results, and an idea of Camillo [75], we prove the theorem stated in the title.     

Subgroups generated by root-elements of groups generated byk-root subgroups

LetG be a Chevalley group over the fieldk and the class of long root subgroups ofG or an abstract group generated by a class of k-root subgroups. Then elements ofA, A are called root-elements. This paper is concerned with the question, whether a subgroupU ofG generated by root-elements is already generated byl-root subgroups,l a subfield ofk. Especially if it is shown that this is the case, whenU is a fixpoint subgroup under some set of automorphisms.     

Finitely generated submodules of differentiable functions II

Let [$\text{E}$(Ω)]^p be the Cartesian product of the space of real-valued infinitely differentiable functions on a connected open set Ω in $\text{R}$ⁿ with itself p-times. The finitely generated submodules of [$\text{E}$(Ω)]^p are of the form im(F) where F: [$\text{E}$(Ω)]^q → [$\text{E}$(Ω)]^p is a p × q matrix of infinitely differentiable functions on Ω. Let $\text{r =}\text{max}\text{{}\text{rank}\text{(F(x)): x ? Ω}}$. The main results of the present paper are that for Ω ? $\text{R}$ⁿ, if the finitely generated submodule im(F) is closed in [$\text{E}$(Ω)]^p, then for every x?ω with rank(F(x)) < r there exists an r × r sub-matrix A of F such that x is a zero of finite order of det(A), and for Ω ? $\text{R}$¹ the converse also holds.     

Irreducible factorizations of rationalq-parameter matrices

This paper considers rational q-parameter matrices (i.e., matrices the entries of which are ratios of scalar polynomials in q variables) and extends the previous results of the authors. Bibliography: 8 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 248, 1998, pp. 147–164. Translated by V. N. Kublanovskaya.     

不可约矩阵的弱指数

作者与Ｒ．Ａ．Ｂｒｕａｌｄｉ教授提出了不可约矩阵弱指数的概念（见［Ｂｒｕｌｉｕ２］）．本文给出了弱指数（弱本原指数，弱完全不可分解指数，弱Ｈａｌｌ指数）的上确界以及它们的指数集．