Large sets of Hamilton cycle and path decompositions

The existence spectrums for large sets of Hamilton cycle decompositions and Hamilton path decompositions are completed. Also, we show that the completion of large sets of directed Hamilton cycle decompositions and directed Hamilton path decompositions depends on the existence of certain special tuscan squares. Several conjectures about special tuscan squares are posed.     

Adaptive Fourier decomposition of functions in quaternionic Hardy spaces

We study decompositions of functions in the Hardy spaces into linear combinations of the basic functions in the orthogonal rational systems B_n, which are obtained in the respective contexts through Gram–Schmidt orthogonalization process on shifted Cauchy kernels. Those lead to adaptive decompositions of quaternionic‐valued signals of finite energy. This study is a generalization of the main results of the first author's recent research in relation to adaptive Takenaka–Malmquist systems in one complex variable. Copyright © 2011 John Wiley & Sons, Ltd.     

On uniqueness of JSJ decompositions of finitely generated groups

We give an example of two JSJ decompositions of a group that are not related by conjugation, conjugation of edge-inclusions, and slide moves. This answers the question of Rips and Sela stated in [RS].On the other hand we observe that any two JSJ decompositions of a group are related by an elementary deformation, and that strongly slide-free JSJ decompositions are genuinely unique. These results hold for the decompositions of Rips and Sela, Dunwoody and Sageev, and Fujiwara and Papasoglu, and also for accessible decompositions.     

Undominated d.c. Decompositions of Quadratic Functions and Applications to Branch-and-Bound Approaches

In this paper we analyze difference-of-convex (d.c.) decompositions for indefinite quadratic functions. Given a quadratic function, there are many possible ways to decompose it as a difference of two convex quadratic functions. Some decompositions are dominated, in the sense that other decompositions exist with a lower curvature. Obviously, undominated decompositions are of particular interest. We provide three different characterizations of such decompositions, and show that there is an infinity of undominated decompositions for indefinite quadratic functions. Moreover, two different procedures will be suggested to find an undominated decomposition starting from a generic one. Finally, we address applications where undominated d.c.d.s may be helpful: in particular, we show how to improve bounds in branch-and-bound procedures for quadratic optimization problems.     

Atomic decompositions of Banach lattice-valued martingales

In this paper, atomic decompositions of Banach lattice-valued martingales are given. We discuss the relation between the LERMT property and atomic decompositions. With the help of atomic decompositions, the relation of the martingale spaces is investigated.     

Primary Decompositions for Left Noetherian Rings

Two constructions are given that describe respectively all shortest primary decompositions and all shortest uniform decompositions for left Noetherian rings. They show that these decompositions are, in general, highly non-unique.     

Isomorphic Schauder decompositions in certain Banach spaces

We extend a theorem of Kato on similarity for sequences of projections in Hilbert spaces to the case of isomorphic Schauder decompositions in certain Banach spaces. To this end we use ?_ψ-Hilbertian and ∞-Hilbertian Schauder decompositions instead of orthogonal Schauder decompositions, generalize the concept of an orthogonal Schauder decomposition to the case of Banach spaces and introduce the class of Banach spaces with Schauder-Orlicz decompositions. Furthermore, we generalize the notions of type, cotype, infratype and M-cotype of a Banach space and study the properties of unconditional Schauder decompositions in Banach spaces possessing certain geometric structure.     

二维气体动力学中压差方程的特征分解和简单波

利用直接的方法讨论了在自相似平面上气体动力学中二维压差方程的特征分解理论,得到了压强P和特征值A±的特征分解.进一步地,若流动来自常状态,还可得到速度（u,v）的特征分解.由此,可以得到与常状态流动相邻的流动是简单波,并说明了简单波的流动区域是被一族直线所覆盖,且沿着每条直线, （P,u,v）为常数.     

Atomic decompositions of martingale hardy–morrey spaces

We establish the atomic decompositions of martingale Hardy– Morrey spaces. The martingale Hardy–Morrey spaces are generalizations of martingale Hardy spaces. Therefore, the atomic decompositions presented in this paper are extensions of the atomic decompositions of martingale Hardy spaces.     

Computing combinatorial decompositions of rings

Using Buchberger's Gröbner basis theory, we obtain explicit algorithms for computing Stanley decompositions, Rees decompositions and Hironaka decompositions of commutative Noetherian rings. These decompositions are of considerable importance in combinatorics, in particular in the theory of Cohen-Macaulay complexes. We discuss several applications of our methods, including a new algorithm for finding primary and secondary invariants of finite group actions on polynomial rings.Research supported by the Institute for Mathematics and its Applications, Minneapolis, with funds provided by the National Science Foundation     

On transitive decompositions of disconnected graphs

We investigate transitive decompositions of disconnected graphs, and show that these behave very differently from a related class of algebraic graph decompositions, known as homogeneous factorisations. We conclude that although the study of homogeneous factorisations admits a natural reduction to those cases where the graph is connected, the study of transitive decompositions does not.     

Banach空间上Banach框架和原子分解的扰动

框架扰动是框架理论中活跃的研究方向, 但它的多数研究是在Hilbert空间上进行的. 该文讨论Banach空间上Banach框架和原子分解的扰动, 得到一些新的结果, 并表明众多已知结果是这些新结果的特例.     

Wavelet compression and nonlinearn-widths

It is shown that certain algorithms of compression based on wavelet decompositions are optimal in the sense of nonlinearn-widths.This research was supported by the Office of Naval Research Contract N0014-91-J1343 and a Binational Science Foundation Grant 89-00505.This research was completed while D. Leviatan and V.M. Tikhomirov were visiting scholars at the University of South Carolina.     

Error analysis of an algorithm for solving an underdetermined linear system

Summary The accumulation of rounding errors in a method used to compute the solution of an underdetermined system of linear equations at the least distance from a given point is being studied. The method used is based on orthogonal matrix decompositions.This research was partially supported by the Progetto Finalizzato Informatica of the Italian National Research Council     

Equivariant primary decomposition and toric sheaves

We study global primary decompositions in the category of sheaves on a scheme which are equivariant under the action of an algebraic group. We show that equivariant primary decompositions exist if the group is connected. As main application we consider the case of varieties which are quotients of a quasi-affine variety by the action of a diagonalizable group and thus admit a homogeneous coordinate ring, such as toric varieties. Comparing these decompositions with primary decompositions of graded modules over the homogeneous coordinate ring, we show that these are equivalent if the action of the diagonalizable group is free. We give some specific examples for the case of toric varieties.     

Functorial homotopy decompositions of looped co-H spaces

In recent work of the first and third authors, functorial coalgebra decompositions of tensor algebras were geometrically realized to give functorial homotopy decompositions of loop suspensions. Later work by all three authors generalized this to functorial decompositions of looped coassociative co-H spaces. In this paper we use different methods which allow for the coassociative hypothesis to be removed.     

Structural decompositions of multivariate distributions with applications in moment and cumulant

We provide lattice decompositions for multivariate distributions. The lattice decompositions reveal the structural relationship between the Lancaster/Bahadur model and the model of Streitberg (Ann. Statist. 18 (1990) 1878). For multivariate categorical data, the decompositions allows modeling strategy for marginal inference. The theory discussed in this paper illustrates the concept of reproducibility, which was discussed in Liang et al. (J. Roy. Statist. Soc. Ser. B 54 (1992) 3). For the purpose of delineating the relationship between the various types of decompositions of distributions, we develop a theory of polytypefication, the generality of which is exploited to prove results beyond interaction.     

Invariant Maximal Positive Subspaces and Polar Decompositions

It is proved that invertible operators on a Krein space which have an invariant maximal uniformly positive subspace and map its orthogonal complement into a nonnegative subspace allow polar decompositions with additional spectral properties. As a corollary, several classes of Krein space operators are shown to allow polar decompositions. An example in a finite dimensional Krein space shows that there exist dissipative operators that do not allow polar decompositions.     

Submeasures and decomposition of measures

Using submeasures and Boolean spaces, new proofs are given for Hewitt-Yosida type decompositions of group-valued exhaustive measures; these give new insight into these decompositions.