Approximative compactness of the algebraic sum of sets

Let X be a group with an invariant metric, A and B nonempty subsets of X with B compact. It is proved that if A is an existence set [1] (approximatively compact [2]) then A + B and B + A are existence sets (approximatively compact). An example is given of a one-dimensional linear metric space (with an invariant metric) in which there exist an approximatively compact set A and an element v such that A + v is not an existence set.Translated from Matematicheskie Zametki, Vol. 23, No. 1, pp. 55–60, January, 1978.     

Weyl型代数的环论性质

设A是代数闭域k上有单位元1的交换结合代数，D是A的交换κ-导子组成的非零k-向量空间，苏育才与赵开明引进Weyl型代数A[D]并且证明了结合代数A[D]是单代数当且仅当A是D-单的且k1[D]在A上的作用为忠实的,通过证明A[D]与smash product A#U(D)同构，我们给出了这一结果的一个纯环论的证明，同时给出了A[D]的一个Ore扩张实现。     

In honour of professor Solomon G. Mikhlin on the occasion of his seventieth birthday

The system identification problem, within the context of this paper, is the determination of an input-output operator A based upon a limited amount of information. We consider the case where A is a linear, time invariant map on an appropriate function space and develop an algorithm for determining A from knowledge of input-output pairs in A.     

An iterative penalty method for a nonlinear problem of equilibrium of a Timoshenko-type plate with a crack

A variational problem of equilibrium of an elastic Timoshenko-type plate in a domain with a slit is considered. A nonpenetration boundary condition in the form of an inequality is specified on the edges of the slit. A penalized equation and an iterative linear equation in integral and differential forms are constructed. Some results on solution convergence and an error estimate are obtained.     

符号空间有限型子转移混沌集的Hausdorff测度与Parry测度

设A是一个每列至少有二个元素为1的不可约0，1方阵，(∑4，σA)为由A所决定的符号空间有限型子转移．在∑A上定义一个与其拓扑相容的度量d使得(∑A，d)的Hausdorff维数为1．若G是H^-可测的σA的Li—Yorke混沌集，则H^1(C)＝0；若A是本原的，则存在一个σA的有限型混沌集S使得H^1(S)＝1，其中H^1为1-维的Hausdorff测度．     

Relations Between Algebras and Their Subalgebras of Invariants

We prove that, if H is a finite-dimensional semisimple Hopf algebra, and A is an FCR H-module algebra over an algebraically closed field, then A is a PI-algebra, provided the subalgebra of invariants is a PI-algebra. We also show that if A is an affine algebra with an action of a finite group G by automorphisms, the subalgebra of the fixed points A^G is in the center of A, and the characteristic of the ground field is either zero or relatively prime to the order of G, then A^G is affine. Analogous results are proved for graded algebras and H-module algebras over a semisimple triangular Hopf algebra over a field of characteristic zero. We prove also that, if A is an H-module algebra with an identity element, and H is either a semisimple group algebra or its dual, then, if A is semiprimitive (semiprime), then so is A^H.     

Hopf代数的半单扩张与不变子环的同调维数

设H是域k上的有限维Hopf代数,A是左H-模代数,AH是A的H-不变子环.假定A/AH是半单扩张且A是平坦的右AH-模.如果H*是unimodular,且存在c∈C(A),使t·c=1.我们证明了WD(AH)=WD(A)=WD(A#H).此外,如果A是投射的左及右AH-模,则有LD(AH)=LD(A)=LD(A#H).     

整环上Moore-Penrose逆的刻画

若A为整环上的n阶可逆矩阵,则X=A-1是满足方程rank■=rank(A)的唯一矩阵.把它推广到满足Rao条件的整环上得到关于矩阵A的Moore-Penrose逆A+的刻画.     

Limits of applicability of a spherical model for solving problems of electroencephalography

Methods are developed for the localization of neuron brain sources with the potential recorded as an electroencephalogram (EEG). A boundary-value problem for a Poisson equation is considered. A boundary Fredholm integral equation of the second kind is deduced. A method for numerically solving an integral equation is proposed, and the results from a number of computing experiments are given.     

Numerical method of solving a linear problem on the minimum of resource consumption

A simple algorithm for developing a quasioptimal control over resource consumption is considered. The control is used as an initial approach to an iterative procedure of computing an optimal control. A system of linear algebraic equations is derived which approximately relate increments of initial conditions of an adjoint system to increments of amplitudes of a quasioptimal control with respect to ultimate values. Local convergence of the computing process with a quadratic rate is proved, and the convergence radius is found. A condition for global convergence of the method is specified.     

模任意子Hopf代数的商余代数的诱导作用

设 Ｈ是域 ｋ上的有限维 Ｈｏｐｆ代数，Ｋ为 Ｈ的任意子 Ｈｏｐｆ代数，Ａ是右 Ｈ－余模代数．设 ＝（Ｈ／Ｋ+ Ｈ）*和，且有 ｃ∈Ａ，ｔ ·ｃ＝１．本 文刻划了 Ａ作为 Ａ＃ *-模的投射性且证明了：如果Ａ／ＡＨ*是 Ｈ-Ｆｒｏｂｅｎｉｕｓ扩张， 则 Ａ ／ＡＨ*是 Ｋ－Ｆｒｏｂｅｎｉｕｓ扩张；如果 Ａ／ＡＨ*是 Ｈ－Ｇａｌｏｉｓ扩张，则 Ａ *／ＡＨ*是 Ｋ－Ｇａｌｏｉｓ扩张．     

Witt型单李超代数

设F是特征p〉2的域,A是F上结合的超交换的代数,D是域为F上A的超交换的导子.设A×D=A[D]为Witt型李超代数.从环论的角度得到了Witt型李超代数为单代数的充分必要条件.     

On the Multiplicity and the Cohen-Macaulayness of Fiber Cones of Graded Modules

Let (A,m) be a Noetherian local ring with maximal ideal m,I an ideal of A,J an m-primary ideal of A,N a finitely generated A-module,S =⊕n≥0 Sn a finitely generated standard graded algebra over A and M =⊕n≥0 Mn a finitely generated graded S-module.We characterize the multiplicity and the Cohen-Macaulayness of the fiber cone FJ(M) =⊕n≥0 Mn/JMn.As an application,we obtain some results on the multiplicity and the Cohen-Macaulayness of the fiber cone ⊕n≥0 InN/JInN.     

Quasi-direct sums of rings and their radicals

Let A, B be rings and P a radical property. Call B an A-Algebra if B is an A-bimodule such that (ba)b₁ = b(ab₁), (bb₁)a = b(b₁a), a(bb₁) = (ab)b₁ for any a ∈ A and any b,b₁ ∈ B. A ring R, written as R = A ? B, is called a quasi-direct sum of (A, B) if A is a subring of R, B is an ideal of R and R is a direct sum of A and B as additive groups. The following results are obtained: 1. A quasi-direct sum of (A, B) is uniquely determined by an A-Algebra B (up to isomorphism); 2. The P-radical of the Algebra B is the same as the P-radical of the ring B; 3. P(A ? B) = P(A) +(B) if and only if P(A)B + BP(A) ? P(B); 4. If B has an identity e then P(A ? B) = P(A)(1?e) + P(B); 5. If P(Z) = 0 for the integer ring Z, then P(M_n(R)) = M_n(P(R)) holds for all rings R if and only if the above equality holds for all unitary rings R. In addition, some relationships of radicals between rings (or algebras over a field, semigroup algebras, etc.) and their corresponding identity extensions are discussed.     

On the embedding of topological domains into quotient fields

Necessary and sufficient conditions to embed a Hausdorff left Ore domain A in a topological field Q(A) of quotients are given in terms of conditions on an invariant uniformity topologizing the multiplicative semigroup A* of A. The categorical aspects of such an embedding are discussed, and a new proof of S. Warner's theorem on the embedding of a left Ore domain as an open subring of a topological field of quotients is given.This work comprises part of the author's doctoral dissertation submitted to SUNY at Buffalo. The author wishes to thank Professor Dov Tamari for suggesting this problem.     

APT环上幂等阵的对角化

设R是一阿贝尔环(R的所有幂等元都在中心里),A是R上的一幂等阵.本文证明了以下结果：(a)A相抵于一对角阵当且仅当A相似于一对角阵;(b)若R是一APT(阿贝尔投射平凡)环,则A在相似变换之下可唯一地化为对角形diag{e₁, ..., e_n｝,这里e_i整除e_i+1;(c)R是APT环当且仅当R/I是APT环,这里I是环R的一幂零理想.由(a),还证明了分离的阿贝尔正则环是APT环.     

非负不可约矩阵的广义Perron补矩阵

1989年Meyor为计算马尔可夫链的平稳分布向量构造了一个算法，首次提出非负不可约矩阵的Perron补矩阵的概念，本给出非负不可约矩阵A的广义Perron补矩阵若干性质，并且证明若矩阵A是不可约逆M-矩阵，其广义Perron补矩阵也是不可约逆M-矩阵。     

Strong conjugation actions induced by flags of exact Borel subalgebras

Let A be a quasi-hereditary algebra with a strong exact Borel subalgebra. It is proved that for any standard semisimple subalgebra T there exists an exact Borel subalgebra B of A such that T is a maximal semisimple subalgebra of B. It is shown that the maximal length of flags of exact Borel subalgebras of A is the difference of the radium and the rank of Grothendic group of A plus 2. The number of conjugation-classes of exact Borel subalgebras is 1 if and only if A is basic; the number is 2 if and only if A is semisimple. For all other cases, this number is 0 or no less than 3. Furthermore, it is shown that all the exact Borel subalgebras are idempotent-conjugate to each other, that is, for any exact Borel subalgebras B and C of A, there exists an idempotent e of A, and an invertible element u of A, such that eBe = u^-1eCeu.     

阿贝尔群与极大类p-群的半直积的Coleman自同构

设G=A\×P是阿贝尔群$A$与极大类p -群P的半直积,其中P中的元以幂自同构的方式作用于A. 该文证明了G的每个Coleman自同构都是内自同构.作为该结果的一个直接推论, 作者得到了这样的群$G$有正规化子性质.     

Characterization of reducible hexagons and fast decomposition of elementary benzenoid graphs

A benzenoid graph is a finite connected plane graph with no cut vertices in which every interior region is bounded by a regular hexagon of a side length one. A benzenoid graph G is elementary if every edge belongs to a 1-factor of G. A hexagon h of an elementary benzenoid graph is reducible, if the removal of boundary edges and vertices of h results in an elementary benzenoid graph. We characterize the reducible hexagons of an elementary benzenoid graph. The characterization is the basis for an algorithm which finds the sequence of reducible hexagons that decompose a graph of this class in O(n²) time. Moreover, we present an algorithm which decomposes an elementary benzenoid graph with at most one pericondensed component in linear time.