用矩阵的初等变换解矩阵方程A_(m×n)X_(n×s)=B_(m×s)

本文通过对一般的矩阵方程Ａｍ×ｎＸｎ×ｓ＝Ｂｍ×ｓ的矩阵Ａ和Ｂ作初等行变换及初等列变换，给出了一般矩阵方程的求解方法．     

用矩阵的初等行变换解矩阵方程X_(m×n)A_(n×s)=B_(m×s)

设矩阵方程为X_(m×n)A_(n×s)=B_(m×s) (1)本文运用矩阵的初等行变换给出了解矩阵方程(1)的一个简便方法。对于矩阵方程(1),我们给出了下面的定理1 矩阵方程(1)有解的充要条件是     

Maximal subalgebras of rank n −1 of the algebra AP(1, n) and reduction of nonlinear wave equations. I

The concept of canonical decomposition of an arbitrary subalgebra of the algebraAO(1,n) is introduced. With the help of this decomposition all maximal subalgebras L of rankn–1 of the algebraAP(1,n), satisfying the conditionL V=1,...;P _n>, whereV=<P ₀,P ₁,...,P ₁> is the space of translation are described.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 11, pp. 1552–1559, November, 1990.     

Minimal Covers of Q +(2n + 1, q) by (n − 1)-Dimensional Subspaces

A t-cover of a quadric is a set C of t-dimensional subspaces contained in such that every point of is contained in at least one element of C.We consider (n – 1)-covers of the hyperbolic quadric Q ⁺(2n + 1, q). We show that such a cover must have at least q ^{n + 1} + 2q + 1 elements, give an example of this size for even q and describe what covers of this size should look like.     

The local rank of an ergodic symmetric power T ⊙n does not exceed n!n −n

The infinity of the rank of ergodic symmetric powers of automorphisms of the Lebesgue space is proved, and sharp upper bounds for their local rank are found.     

Naturally graded Leibniz algebras with characteristic sequence (n − m, m)

We consider the classification problem for special classes of nilpotent Leibniz algebras. Namely, we consider “naturally” graded nilpotent n-dimensional Leibniz algebras for which the right multiplication operator (by the generic element) has two Jordan blocks of dimensionsm and n ? m. Earlier, the problem of classifying such algebras was studied form < 4. The present paper continues these studies for the case m ≥ 4.     

A new proof of the existence of (q 2−q+1)-arcs inPG(2,q 2)

Journal of Geometry -     

Regularity and explicit representation of (0,1,...,m−2,m) interpolation on the zeros of (1−x 2)P n −2/(α,β) (x)

Necessary and sufficient conditions for the regularity andq-regularity of (0,1,...,m–2,m) interpolation on the zeros of (1–x ²)P _n ^–2/(,) (x) (,>–1) in a manageable form are established, whereP _n ^–2/(,) (x) stands for the (n–2)th Jacobi polynomial. Meanwhile, the explicit representation of the fundamental polynomials, when they exist, is given. Moreover, we show that under a mild assumption if the problem of (0,1,...,m–2,m) interpolation has an infinity of solutions then the general form of the solutions isf ₀(x)+C f(x) with an arbitrary constantC.This work is supported by the National Natural Science Foundation of China.     

Jackson-Type Inequalities in the Spaces S(p,q) (σm−1)

Mathematical Notes - In the case of approximation of functions by using linear methods of summation of their Fourier-Laplace series in the spaces S(p,q) (σm?1), m ≥ 3, for classes...     

On the intrinsic normalizations of the seminonholonomic complexesSN Gr(m, n, (m+1)(n−m)−ϱ). I

Some intrinsic normalizations of seminonholonomic complexes of then-dimensional projective space are considered. Vilnius University, Naugarduko 24, 2006 Vilnius, Lithuania. Translated from Lietuvos Matematikos Rinkinys, Vol. 39, No. 4, pp. 517–538, October–December, 1999. Translated by R. Lapinskas     

On the rank of 3×3×3-tensors

Let U, V and W be finite dimensional vector spaces over the same field. The rank of a tensor τ in U???V???W is the minimum dimension of a subspace of U???V???W containing τ and spanned by fundamental tensors, i.e. tensors of the form u???v???w for some u in U, v in V and w in W. We prove that if U, V and W have dimension three, then the rank of a tensor in U???V???W is at most six, and such a bound cannot be improved, in general. Moreover, we discuss how the techniques employed in the proof might be extended to prove upper bounds for the rank of a tensor in U???V???W when the dimensions of U, V and W are higher.     

The rank of a 2 × 2 × 2 tensor

As computing power increases, many more problems in engineering and data analysis involve computation with tensors, or multi-way data arrays. Most applications involve computing a decomposition of a tensor into a linear combination of rank-1 tensors. Ideally, the decomposition involves a minimal number of terms, i.e. computation of the rank of the tensor. Tensor rank is not a straight-forward extension of matrix rank. A constructive proof based on an eigenvalue criterion is provided that shows when a 2?×?2?×?2 tensor over ? is rank-3 and when it is rank-2. The results are extended to show that n?×?n?×?2 tensors over ? have maximum possible rank n?+?k where k is the number of complex conjugate eigenvalue pairs of the matrices forming the two faces of the tensor cube.