On Certain Commutator Estimates for Vector Fields

A unifying approach for proving certain commutator estimates involving smooth, not-necessarily divergence-free vector fields is introduced and implemented in the scales of weighted Triebel–Lizorkin and Besov spaces and certain variable exponent Triebel–Lizorkin and Besov spaces. Such commutator estimates are motivated by the study of well-posedness results for some models in incompressible fluid mechanics.     

On Sums of Vector Fields

We discuss one case where the integration of a sum of vector fields is reducible to the integration of the summands. Applications include the construction of a class of additive group actions on affine space and a proof that these are stably tame, and also the explicit solution of a class of differential equations from mathematical biology.     

线性l1模极小化问题的熵函数延拓法

本文通过利用极大熵函数构造同伦映射，建立了求解无约束线性l1模问题的熵函数延拓算法，证明了方法的收敛性，并给出了数值算例．     

On Waring's Problem in Number Fields

Let K be an algebraic number field of degree n over the rationals,and denote by J_k the subring of K generated by the kth powersof the integers of K. Then G_K(k) is defined to be the smallests1 such that, for all totally positive integers vJ_k of sufficientlylarge norm, the Diophantine equation (1.1) is soluble in totally non-negative integers _i of K satisfying N(_i)<<N(v)^1/k (1is). (1.2) In (1.2) and throughout this paper, all implicit constants areassumed to depend only on K, k, and s. The notation G_K(k) generalizesthe familiar symbol G(k) used in Waring's problem, since wehave G_Q(k) = G(k). By extending the Hardy–Littlewood circle method to numberfields, Siegel [8, 9] initiated a line of research (see [1–4,11]) which generalized existing methods for treating G(k). Thistypically led to upper bounds for G_K(k) of approximate strengthnB(k), where B(k) was the best contemporary upper bound forG(k). For example, Eda [2] gave an extension of Vinogradov'sproof (see [13] or [15]) that G(k)(2+o(1))k log k. The presentpaper will eliminate the need for lengthy generalizations assuch, by introducing a new and considerably shorter approachto the problem. Our main result is the following theorem.     

Partial Minimization for Vector Variational Problems

The basic idea of performing a partial minimization with respect to some components in a vector variational problem, while keeping the other fixed, is explored and implemented in various examples. In one-dimensional problems, it leads sometimes to nonstandard variational problems. We also include a situation for a genuine vector variational problem coming from the reformulation of some optimal design problems in conductivity.     

On the Leibniz Cohomology of Vector Fields

Gelfand and Fuks have studied the cohomology of the Lie algebra of vector fields on a manifold. In this article, we generalize their main tools to compute the Leibniz cohomology, by extending the two spectral sequences associated to the diagonal and the order filtration. In particular, we determine some new generators for the diagonal Leibniz cohomology of the Lie algebra of vector fields on the circle.     

On Trajectories of Analytic Gradient Vector Fields

Let f:Rⁿ,0→R,0 be an analytic function defined in a neighbourhood of the origin, having a critical point at 0. We show that the set of non-trivial trajectories of the equation xdot;=∇f(x) attracted by the origin has the same ?ech-Alexander cohomology groups as the real Milnor fibre of f.     

Bi-center Problem in a Class of Z2-equivariant Quintic Vector Fields

In this paper, we study the center problem for Z2-equivariant quintic vector ?elds. First of all, for convenience in analysis, the system is simpli?ed by using some transformations. When the system has two nilpotent points at (0,±1) with multiplicity three, the ?rst seven Lyapunov constants at the singular points are calculated by applying the inverse integrating factor method. Then, ?fteen center conditions are obtained for the two nilpotent singular points of the system to be centers, and the su?ciency of the ?rst seven center conditions are proved. Finally, the ?rst ?ve Lyapunov constants are calculated at the two nilpotent points (0,±1) with multiplicity ?ve by using the method of normal forms, and the center problem of this system is partially solved.     

L旋转向量场中奇点的运动

本文引入Ｌ旋转向量场的定义，给出奇点随参数移动的Ｌ旋转向量场中奇点移动的条件     

On a Problem of Hasse for Certain Imaginary Abelian Fields

Let K be the composite field of an imaginary quadratic field Q(ω) of conductor d and a real abelian field L of conductor f distinct from the rationals Q, where (d,f)=1. Let Z_K be the ring of integers in K. Then concerning to Hasse's problem we construct new families of infinitely many fields K with the non-monogenic phenomena (1), (2) which supplement (J. Number Theory23 (1986), 347-353; Publ. Math. Fac. Sci Besançon, Theor. Nombres (1984) 25pp) and with monogenic (3).     

平衡问题变分包含问题及不动点问题的二次极小化

借助预解式技巧,寻求二次极小化问题minx∈Ω‖x‖2的解,其中Ω是Hilbert空间中某一广义平衡问题的解集,与一无穷族非扩张映像的公共不动点的集合,以及某一变分包含的解集的交集．在适当的条件下,逼近上述极小化问题的解的一新的强收敛定理被证明．     

On the Vanishing Orders of Vector Fields on Fano Varieties of Picard Number 1

We show that the vanishing order of a non-zero vector field at a generic point of a smooth Fano variety of Picard number 1 cannot exceed the dimension of the Fano variety. Furthermore, if there exist only finitely many rational curves of minimal degree through a generic point of the Fano variety, we show that a non-zero vector field cannot vanish at a generic point of the Fano variety.     

An $L_1$ Minimization Problem by Generalized Rational Functions

Let $P,Q \subset L_1(X,\Sigma,\mu)$ and $q(x)>0$ a. e. in $X$ for all $q\in Q$. Define $R=\{p/q:p\in P,q\in Q\}$. In this paper we discuss an $L_1$ minimization problem of a nonnegative function $E(z,x)$, i.e. we wish to find a minimum of the functional $\phi(r)=\int _X qE(r,x)d\mu$ form $r=p/q\in R$. For such a problem we have established the complete characterizations of its minimum and of uniqueness of its minimum, when both $P,Q$ are arbitrary convex subsets.     

处理噪声问题的泰勒展开交替最小化算法

为了处理图像、计算机视觉和生物信息等领域中广泛存在的稀疏大噪声和高斯噪声问题,提出了一种利用交替方向最小化思想求解主成分追求松弛模型的泰勒展开交替最小化算法(TEAM).采用推广泰勒展开和收缩算子等技术推导出低秩矩阵和稀疏大噪声矩阵的迭代方向矩阵,加入连续技术提高算法的收敛速率,设计出TEAM算法的求解步骤.实验中,将TEAM算法与该领域的顶级算法作分析对比.结果表明,TEAM算法时间优势明显,误差优势略好.     

On Generalized Integral Means and Euler Type Vector Fields

Formulas for the Euler vector fields, the Neumann derivatives, and the Euler as well as Dirichlet product are derived. Extensions to a Riemann domain of the Gauss operator, the Gauss’ lemma and the related jump formulas are given, and the Gauss–Helmholtz representation with ramifications proved. Examples of elementary solutions to certain modified Laplace operators, applications to pseudospherical harmonics, and characterizations of pseudoradial, pseudospherical, nearly holomorphic, and holomorphic functions, are obtained, and constancy criterion for locally Lipschitz, semiharmonic, respectively, weakly holomorphic functions are given.     

On Boundary Properties of Solutions of Complex Vector Fields

This work presents results on the boundary properties of solutions of a complex, planar, smooth vector field L. Classical results in the H^p theory of holomorphic functions of one variable are extended to the solutions of a class of nonelliptic complex vector fields.     

A Self‐Dual Polar Factorization for Vector Fields

We show that any nondegenerate vector field u in \begin{align*}L^{\infty}(\Omega, \mathbb{R}^N)\end{align*}, where Ω is a bounded domain in \begin{align*}\mathbb{R}^N\end{align*}, can be written as \begin{align*}u(x)= \nabla_1 H(S(x), x)\quad {\text for a.e.\ x \in \Omega}\end{align*}}, where S is a measure‐preserving point transformation on Ω such that \begin{align*}S^2=I\end{align*} a.e. (an involution), and \begin{align*}H: \mathbb{R}^N \times \mathbb{R}^N \to \mathbb{R}\end{align*} is a globally Lipschitz antisymmetric convex‐concave Hamiltonian. Moreover, u is a monotone map if and only if S can be taken to be the identity, which suggests that our result is a self‐dual version of Brenier's polar decomposition for the vector field as \begin{align*}u(x)=\nabla \phi (S(x))\end{align*}, where ? is convex and S is a measure‐preserving transformation. We also describe how our polar decomposition can be reformulated as a (self‐dual) mass transport problem. © 2012 Wiley Periodicals, Inc.     

On the Lattice Approximation for Certain Generalized Vector Markov Fields in Four Spacetime Dimensions

We extend previous results by Albeverio, Iwata and Schmidt on the construction of a convergent lattice approximation for invariant scalar 3-vector generalized random fields F of an infinitely divisible type and apply them to the construction of convergent lattice approximation for the generalized random vector field A determined by the stochastic quaternionic Cauchy–Riemann equation A = F.     

Revisiting the Concentration Problem of Vector Fields within a Spherical Cap: A Commuting Differential Operator Solution

We propose a novel basis of vector functions, the mixed vector spherical harmonics that are closely related to the functions of Sheppard and Török and help us reduce the concentration problem of tangential vector fields within a spherical cap to an equivalent scalar problem. Exploiting an analogy with previous results published by Grünbaum, Longhi and Perlstadt, we construct a differential operator that commutes with the concentration operator of this scalar problem and propose a stable and convenient method to obtain its eigenfunctions. Having obtained the scalar eigenfunctions, the calculation of tangential vector Slepian functions is straightforward.