An Extended Faber Operator

   Abstract. One of the basic tools in the theory of polynomial approximation in the uniform norm on compact plane sets is the Faber operator. Usually, the Faber operator is viewed as an operator acting on functions in the disk algebra, that is, functions which are holomorphic in the open unit disk D and continuous on D. We consider an extended Faber operator acting on arbitrary functions continuous on ; D.     

The Faber Operator and its Boundedness

Let G be a domain bounded by a Jordan curve Γ, and let A(G) be the Banach space of functions continuous on G and holomorphic in G. The Faber operator T is a linear mapping from A( ) to A(G) mapping wⁿ onto the nth Faber polynomial F_n(z) (n=0, 1, 2, …). We show that T<∞ if Γ is piecewise Dini-smooth, and give an example of a quasicircle Γ for which T=∞.     

An algebraic structure for Faber polynomials

Let Σ be the set of functions, convergent for all |z|>1, with a Laurent series of the form f(z)=z+∑_n?0a_nz^-n. In this paper, we prove that the set of Faber polynomial sequences over Σ and the set of their normalized kth derivative sequences form groups which are isomorphic to the hitting time subgroup and the Bell^(k) subgroup of the Riordan group, respectively. Further, a relationship between such Faber polynomial sequences and Lucas and Sheffer polynomial sequences is derived.     

Extended Best Polynomial Approximation Operator in Orlicz Spaces

In this article we consider the best polynomial approximation operator, defined in an Orlicz space L ^Φ(B), and its extension to L ^?(B) where ? is the derivative function of Φ. A characterization of these operators and several properties are obtained.     

Hamilton算子和Laplace算子间的一个积分公式

本文给出了Hamilton算子和Laplace算子间的一个积分公式,并指出文献[1]中的一个错误.     

The Extended Alpha-triple I Algorithm Based on the Generalized Implication Operator

In this paper, the classical implication operator is generalized, and then the definition of generalized implication operator on [0, 1] is proposed. Based on generalized implication operator, the extended alpha-triple I principle is presented by generalizing the alpha-triple I algorithm. By analyzing the essence of alpha-triple Fuzzy Modus Ponens (FMP) and alpha-triple Fuzzy Modus Tollens (FMT) principles, and based on the generalized implication operator, the generalized calculating formula of extended alpha-triple I algorithm is proposed. At the same time, the reversibility on the proposed alpha-triple I algorithm is discussed. It is proved that Compositional Rule of Inference (CRI) is a special case of extended alpha-triple I algorithm. Finally, two implication operations are proposed to validate the proposed generalized equation.     

On Convergence of Extended Dynamic Mode Decomposition to the Koopman Operator

Extended dynamic mode decomposition (EDMD) (Williams et al. in J Nonlinear Sci 25(6):1307–1346, 2015) is an algorithm that approximates the action of the Koopman operator on an N-dimensional subspace of the space of observables by sampling at M points in the state space. Assuming that the samples are drawn either independently or ergodically from some measure \(\mu \), it was shown in Klus et al. (J Comput Dyn 3(1):51–79, 2016) that, in the limit as \(M\rightarrow \infty \), the EDMD operator \(\mathcal {K}_{N,M}\) converges to \(\mathcal {K}_N\), where \(\mathcal {K}_N\) is the \(L_2(\mu )\)-orthogonal projection of the action of the Koopman operator on the finite-dimensional subspace of observables. We show that, as \(N \rightarrow \infty \), the operator \(\mathcal {K}_N\) converges in the strong operator topology to the Koopman operator. This in particular implies convergence of the predictions of future values of a given observable over any finite time horizon, a fact important for practical applications such as forecasting, estimation and control. In addition, we show that accumulation points of the spectra of \(\mathcal {K}_N\) correspond to the eigenvalues of the Koopman operator with the associated eigenfunctions converging weakly to an eigenfunction of the Koopman operator, provided that the weak limit of the eigenfunctions is nonzero. As a by-product, we propose an analytic version of the EDMD algorithm which, under some assumptions, allows one to construct \(\mathcal {K}_N\) directly, without the use of sampling. Finally, under additional assumptions, we analyze convergence of \(\mathcal {K}_{N,N}\) (i.e., \(M=N\)), proving convergence, along a subsequence, to weak eigenfunctions (or eigendistributions) related to the eigenmeasures of the Perron–Frobenius operator. No assumptions on the observables belonging to a finite-dimensional invariant subspace of the Koopman operator are required throughout.     

Inequalities for the Extended Best Polynomial Approximation Operator in Orlicz Spaces

In this paper we pursue the study of the best approximation operator extended from L~Φ to L~φ, where φ denotes the derivative of the function Φ. We get pointwise convergence for the coefficients of the extended best approximation polynomials for a wide class of function f, closely related to the Calder′on–Zygmund class t_m~p(x) which had been introduced in 1961. We also obtain weak and strong type inequalities for a maximal operator related to the extended best polynomial approximation and a norm convergence result for the coefficients is derived. In most of these results, we have to consider Matuszewska–Orlicz indices for the function φ.     

Irreducibility of some Faber polynomials

Apply weight 0 Hecke operators to the modular function j and express the result as a polynomial in j. These polynomials were considered long ago in analysis, and recently attracted the attention of number theorists primarily for their connection with Borcherds’ infinite products. In particular, Ken Ono conjectured that all of them are irreducible. We prove a partial result towards this conjecture by presenting infinite families of these polynomials which are proved to be irreducible. Supported by NSF grant DMS-0501225.     

An Example on Operator Ideals

ＡｎＥｘａｍｐｌｅｏｎＯｐｅｒａｔｏｒＩｄｅａｌｓＺｈｏｎｇＨｕａｉｊｉｅ（钟怀杰）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，ＦｕｊｉａｎＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｆｕｚｈｏｕ，３５０００７）Ａｂｓｔｒａｃｔ：ＬｅｔＸ＝ｌ１＋ｌ２．Ｄ...     

A note on Faber operator

For a rectifable Jordan curve Γ with complementary domainsD and D,Anderson conjectured that the Faber operator is a bounded isomorphism between the Besov spaces Bp(1 p ∞) of analytic functions in the unit disk and in the inner domain D,respectively.We point out that the conjecture is not true in the special case p=2,and show that in this case the Faber operator is a bounded isomorphism if and only if Γ is a quasi-circle.     

关于Faber多项式的一个注记

Faber多项式通常被用来研究单叶函数的性质,同时也提供了用多项式逼近区域内的解析函数的一个有价值的工具.本文给出一个关于∑类单叶函数的Faber多项式递推公式,并由此得到计算Faber系数的新公式,在一定情形下,它比已有的公式更为简单.     

Differential calculus on the Faber polynomials

The Faber polynomials are presented as a coordinate system to study the geometry of the manifold of coefficients of univalent functions.     

关于三个算子的算子不等式(英文)

As a generalization of grand Furuta inequality,recently Furuta obtain：If A≥ B≥0 with A0,then for t∈[0,1]and p1,p2,p3,p4≥1, A t 2[A- t 2{A t 2（A/ t 2 Bp 1A /t2 ）p 2A t 2}p 3A -t2 ]p 4A t 2 1 [{（p1/t）p2＋t}p3-t]p4＋t]≤A. In this paper,we generalize this result for three operators as follow：If A≥B≥C≥0 with B0,t∈[0,1]and p1,p2,···,p2n/1,p2n≥1 for a natural number n.Then the following inequalities hold for r≥t, A1/t＋r≥ [A r 2[B /t 2{B t 2······[B /t 2{B t 2（B /t 2 ←B /t 2 n times Bt 2 n/1 times by turns Cp 1B /t 2）p 2B t 2}p 3B /t 2]p 4···B t 2}p 2n/1B /t 2 B /t 2 n times Bt 2 n/1 times by turns→ ]p 2nA r 2] 1/t＋r q[2n]＋r/t, where q[2n]≡{···[{[（p1-t）p2＋t]p3/t}p4＋t]p5/···/t}p2n＋t /t and t alternately n times appear .     

单位球上μ-Bloch空间之间的加权Cesàro算子

主要讨论了C~n中单位球上空间β_μ到β_ν、β_μ,0到β_ν,0的加权Cesàro算子的有界性和紧性问题,给出了这些空间上加权Cesàro算子有界和紧的充要条件.     

非线性方程的最佳Krawczyk-Hansen算子

提出了求解非线性方程组的最佳Krawczyk-Hansen算子,通过具体算例验证了其最优性.     

An Integral Equality on the Laplace-Beltrami Operator

Let M be an n-dimensional Riemanniaii manifold of class C^r(r> 2)> and D \subset M be a regular oriented domain on M with boundary \partial D, and W_2,0^2(D) denote the Sobolev space defined on D with the property that every u \in W_2,0^2(D) vanishes at \partial D,i. e., $u|_\partial D=0$. Let (\alpha_=\alpha \beta) be the symmetric matrix of the positive definite metric of M,and $\nabla _\alpha$ denote the operator of the covariant derivative with respect to $\alpha _\alpha \beta$. For any $u \in C^\infty(M)$, it is convenient to define $u_\alpha=\nabla_\alpha u,u_\alpha \beta=\nabla_\alpha u_\beta$ $u^\alpha=a^\alpha\beta=a^\alpha\gamma \nabla_\gamma u^\beta.(1 \leq \alpha,\beta,\gamma \leq n)$ In this paper we establish the following Theorem. Let $u \in W_2,0^2(D)$ . Then $\int_D{u^\alpha \beta u_\alpha \beta dV}=\int_D{(\Delta u)^2dV}+\int_D{Ric(du,du)dV}-\int_\partial D{(\nabla_Nu)^2\Omega ds}$ where $\Delta$ is the Laplace-Beltrami operator, Ric (du, du) is the Ricci curvature of M with respect to the vector field du, \nabla_N is the directional derivative in the direction of the exterior normal vector N at $\partial D$ is the mean curvature of \partial D in M.