An inequality for the multivariate normal distribution

Herman Chernoff used Hermite polynomials to prove an inequality for the normal distribution. This inequality is useful in solving a variation of the classical isoperimetric problem which, in turn, is relevant to data compression in the theory of element identification. As the inequality is of interest in itself, we prove a multivariate generalization of it using a different argument.     

半拟三角弱Hopf代数

作为拟三角弱Hopf代数的推广,我们引入了半拟三角弱Hopf代数的概念.令(H,R,v)是一个半拟三角弱Hopf代数,其中,R是其半拟三角结构.我们指明R保持了拟三角弱Hopf代数中泛R-矩阵的许多基本性质.特别地,讨论了Drinfeld元的性质,证明其是可逆的并且是余作用v的余不变量.另外,证明了半拟三角弱Hopf代数的对极平方是对合的.     

Polar decomposition in e-rings

An e-ring is a generalization of the ring of bounded linear operators on a Hilbert space together with the subset consisting of all effect operators on that space. Associated with an e-ring is a partially ordered abelian group, called its directed group, that generalizes the additive group of bounded Hermitian operators on the Hilbert space. We prove that every element of the directed group of an e-ring has a polar decomposition if and only if every element has a carrier projection and is split by a projection into a positive and a negative part.     

弱$r$-Clean环

As generalization of r-clean rings and weakly clean rings, we define a ring R is weakly r-clean if for any a∈R there exist an idempotent e and a regular element r such that a = r + e or a = r-e. Some properties and examples of weakly r-clean rings are given. Furthermore, we prove the weakly clean rings and weakly r-clean rings are equivalent for abelian rings.     

Decomposable subspaces,linear sections of Grassmann varieties,and higher weights of Grassmann codes

We consider the question of determining the maximum number of points on sections of Grassmannians over finite fields by linear subvarieties of the Plücker projective space of a fixed codimension. This corresponds to a known open problem of determining the complete weight hierarchy of linear error correcting codes associated to Grassmann varieties. We recover most of the known results as well as prove some new results. A basic tool used is a characterization of decomposable subspaces of exterior powers, that is, subspaces in which every nonzero element is decomposable. Also, we use a generalization of the Griesmer–Wei bound that is proved here for arbitrary linear codes.     

Simplicial gauge theory on spacetime

We define a discrete gauge-invariant Yang–Mills–Higgs action on spacetime cylindrical meshes with simplicial spatial base. The formulation is a generalization of classical lattice gauge theory, and we prove consistency of the action in the finite element sense. In addition, we perform numerical tests of convergence towards exact continuum results for several choices of gauge fields in pure gauge theory.     

An overlapping domain decomposition preconditioner for a class of discontinuous Galerkin approximations of advection-diffusion problems

We consider a scalar advection-diffusion problem and a recently proposed discontinuous Galerkin approximation, which employs discontinuous finite element spaces and suitable bilinear forms containing interface terms that ensure consistency. For the corresponding sparse, nonsymmetric linear system, we propose and study an additive, two-level overlapping Schwarz preconditioner, consisting of a coarse problem on a coarse triangulation and local solvers associated to a family of subdomains. This is a generalization of the corresponding overlapping method for approximations on continuous finite element spaces. Related to the lack of continuity of our approximation spaces, some interesting new features arise in our generalization, which have no analog in the conforming case. We prove an upper bound for the number of iterations obtained by using this preconditioner with GMRES, which is independent of the number of degrees of freedom of the original problem and the number of subdomains. The performance of the method is illustrated by several numerical experiments for different test problems using linear finite elements in two dimensions.

     

On the quadratic convergence of the Jabobi method for normal matrices

It has recently been proved that the Jacobi method for computing eigenvalues and eigenvectors of real symmetric matrices after a certain stage in the process converges quadratically ([3], [4]). The purpose of this paper is to prove that this also applies to the generalization of the Jacobi method for general normal matrices due to Goldstine and Horwitz [2]. We restrict ourselves to the special row cyclic method of enumerating pivot elements, but it is believed that also other kinds of enumeration will give similar results. The proof consists of two parts; in the first part we show that under certain conditions the pivot element chosen is nearly annihilated, and in the second part we use this to study what happens with the off-diagonal elements after a whole sweep has been performed.     

Dimension theory for generalized effect algebras

In this paper, we define and study dimension generalized effect algebras (DGEAs), i.e., Dedekind orthocomplete and centrally orthocomplete generalized effect algebras equipped with a dimension equivalence relation. Our theory is a bona fide generalization of the theory of dimension effect algebras (DEAs), i.e., it is formulated so that if a DGEA happens to be an effect algebra (i.e., it has a unit element), then it is a DEA. We prove that a DGEA decomposes into type I, II, and III DGEAS in a manner analogous to the type I/II/III decomposition of a DEA.     

A Class of Solvable Lie Algebras with Triangular Decompositions

So far there has been elementary proof for Frobenius's theorem only in special cases: if the complement is solvable, see e.g. [3], if the complement is of even order, see e.g. [6]. In the first section we consider the case, when the order of the complement is odd. We define a graph the vertices of which are the set K^# of elements of our Frobenius group with 0 fixed points. Two vertices are connected with an edge if and only if the corresponding elements commute. We prove with elementary methods that K is a normal subgroup in G if and only if there exists an element x in K^# such that all elements of K^# belonging to the connected component C of K^# containing x are at most distance 2 from c and N^G(C) is not a -group, where is the set of prime divisors of the Frobenius complement of G. In the second section we generalize the case when the order of the complement is even, proving that the Frobenius kernel is a normal subgroup, if a fixed element a of the complement, the order of which is a minimal prime divisor of the order of the complement, generates a solvable subgroup together with any ofits conjugates. In the third section we prove a generalization of the Glauberman-Thompson normal p-complement theorem, and using this wegive another sufficient condition for the Frobenius kernel to be a normal subgroup for |G| odd, namely we prove this under the conditionthat all the Sylow normalizers in G intersect some of the complements     

高维Klein群的一个不等式及其应用

本文首先得到了SL（2，Гn）中Klein群的一个不等式，并给出了它的两个应用；然后证明了对SL（2，Гn）中的非初等群G，若G中的任意斜驶元素f满足tr^2（f）〉4且当∞ 不属于fix（f）时tr（f）=tr（f），则存在h∈SL（2，Гn）使得hGh^-1属于SL（2，R），此结果是Maskit相关结果的推广。     

Pfaffian labelings and signs of edge colorings

We relate signs of edge-colorings (as in classical Penrose’s result) with “Pfaffian labelings”, a generalization of Pfaffian orientations, whereby edges are labeled by elements of an Abelian group with an element of order two. In particular, we prove a conjecture of Goddyn that all k-edge-colorings of a k-regular Pfaffian graph G have the same sign. We characterize graphs that admit a Pfaffian labeling in terms of bricks and braces in their matching decomposition and in terms of their drawings in the projective plane. Partially supported by NSF grants 0200595 and 0354742.     

On partitions of a partially ordered set

Using linear programming we prove a generalization of Greene and Kleitman's generalization of Dilworth's theorem on the decomposition of a partially ordered set into chains.     

Generating functions for multi-labeled trees

Multi-labeled trees are a generalization of phylogenetic trees that are used, for example, in the study of gene versus species evolution and as the basis for phylogenetic network construction. Unlike phylogenetic trees, in a leaf-multi-labeled tree it is possible to label more than one leaf by the same element of the underlying label set. In this paper we derive formulae for generating functions of leaf-multi-labeled trees and use these to derive recursions for counting such trees. In particular, we prove results which generalize previous theorems by Harding on so-called tree-shapes, and by Otter on relating the number of rooted and unrooted phylogenetic trees.     

A note on harmonic forms on complete manifolds

In this note, we will prove that under certain conditions, the space of polynomial growth harmonic functions and harmonic forms with a fixed growth rate on manifolds which are asymptotically nonnegatively curved is finite dimensional. This is a partial generalization of the works of Li and Colding-Minicozzi. We will also give an explicit estimate for the dimension in case the manifold is a complete surface of finite total curvature. This is a generalization to harmonic forms of the work of Li and the author.

     

Dimension subgroups and<Emphasis Type="Italic">p</Emphasis>-th powers in<Emphasis Type="Italic">p</Emphasis>-groups

We prove that if the nilpotence class of ap-group is strictly less thanp ^kthen every product ofp ^k-thpowers can be written as thep-th power of an element. Scoppola and Shalev have proven the same thing for groups of class strictly less thanp ^k−p ^k−1. They also provide an example which proves that ours is the best possible result. This is a generalization of the well known fact that in groups of class strictly less thanp every product ofp-powers is again ap-th power. Along the way we prove results of independent interest on dimension subgroups ofp-groups.     

A note on log etale Čech cohomolog

In this paper, we prove the comparison theorem between log etale cohomology and log etale Čech cohomology for certain log schemes, which is a generalization of a result of Artin on the comparison theorem between etale cohomology and etale Čech cohomology. It turns out that the naive generalization is not true, and we also give a counter-example for it. Received: 2 July 2000 / Revised version: 4 September 2000     

Very Colorful Theorems

We prove several colorful generalizations of classical theorems in discrete geometry. Moreover, the colorful generalization of Kirchberger’s theorem gives a generalization of the theorem of Tverberg on non-separated partitions.     

The dual quasisemigroup and controllability of evolution equations

We study the notion of dual quasisemigroups of bounded linear operators as a generalization of that for strongly continuous semigroup and prove some properties similar to the dual of a semigroup, among other things we prove that for reflexive Banach spaces the dual quasisemigroup is strongly continuous on (0,+∞). This allows us to extend some recent criteria of controllability to a general class of evolution equations in reflexive Banach spaces.     

Consistency of kernel‐based quantile regression

Quantile regression is used in many areas of applied research and business. Examples are actuarial, financial or biometrical applications. We show that a non‐parametric generalization of quantile regression based on kernels shares with support vector machines the property of consistency to the Bayes risk. We further use this consistency to prove that the non‐parametric generalization approximates the conditional quantile function which gives the mathematical justification for kernel‐based quantile regression. Copyright © 2008 John Wiley & Sons, Ltd.