Approximation Properties of Recursively Defined Bernstein-Type Operators

We consider a generalization of classical Bernstein operators obtained by replacing the binomial coefficients with general ones satisfying a suitable recursive relation. We study the uniform convergence of these operators together with some quantitative estimates and regularity properties. Finally, in some particular cases, we investigate the behavior of the iterates.     

Multianisotropic Integral Operators Defined by Regular Equations

Siberian Mathematical Journal - The article continues the authors’ previous research, where they are proved the well-posed solvability of regular equations in ℝn and the Dirichlet...     

Convergence in Variation for Bernstein-Type Operators

In this paper, we deal with Bernstein-type operators defined by Cárdenas-Morales et al. as \({B_{n}(f \circ \tau^{-1}) \circ \tau}\), where \({B_{n}}\) is the nth Bernstein polynomial (Comput Math Appl 62(1):158–163, 2011). Assuming that \({\tau}\) and f are absolutely continuous functions on \({[0, 1]}\) and inf \({\tau ^{\prime} (x) \geq m > 0}\) as well as \({\tau (0) = 0}\) and \({\tau (1) = 1,}\) we study the convergence of Bernstein-type operators to f in variation seminorm. Moreover, we give a Voronovskaja-type formula and a Jackson-type estimate in the sense of Bardaro et al. (Analysis 23:299–340, 2003).     

Bernstein-Type Operators on the Half Line

We define Bernstein-type operators on the half line [0, +[ by means of two sequences of strictly positive real numbers. After studying their approximation properties, we also establish a Voronovskaja-type result with respect to a suitable weighted norm.     

Lower Estimates for Centered Bernstein-Type Operators

We obtain converse inequalities of type A in the uniform distance for centered Bernstein-type operators in terms of suitable Ditzian—Totik moduli of smoothness. We use probabilistic representations of the operators in terms of stochastic processes as well as approximation-theoretic techniques. October 16, 2000. Date revised: January 15, 2001. Date accepted: March 12, 2001.     

On Certain Best Constants for Bernstein-Type Operators

We discuss the generalized version of a best-constant problem raised by Z. Li in a note which recently appeared in Journal of Approximation Theory. Some best constants for well known Bernstein-type operators are obtained.     

Upper Estimates in Direct Inequalities for Bernstein-Type Operators

We obtain explicit upper estimates in direct inequalities with respect to the usual sup-norm distance for Bernstein-type operators. Our approach combines analytical and probabilistic techniques based on representations of the operators in terms of stochastic processes. We illustrate our results by considering some classical families of operators, such as Weierstrass, Szàsz, and Bernstein operators.     

Exponential Stability for Discrete Time Linear Equations Defined by Positive Operators

In this paper the problem of exponential stability of the zero state equilibrium of a discrete-time time-varying linear equation described by a sequence of linear positive operators acting on an ordered finite dimensional Hilbert space is investigated. The class of linear equations considered in this paper contains as particular cases linear equations described by Lyapunov operators or symmetric Stein operators as well as nonsymmetric Stein operators. Such equations occur in connection with the problem of mean square exponential stability for a class of difference stochastic equations affected by independent random perturbations and Markovian jumping as well us in connection with some iterative procedures which allow us to compute global solutions of discrete time generalized symmetric or nonsymmetric Riccati equations. The exponential stability is characterized in terms of the existence of some globally defined and bounded solutions of some suitable backward affine equations (inequalities) or forward affine equations (inequalities).     

Poisson Equations Associated with Differential Second Quantization Operators in White Noise Analysis

In this paper we shall show the heredity of a differentiable one-parameter semigroup under the second quantization and then discuss the resolvent of the differential second quantization operator and the potentials of test white noise functionals. As an application, we shall investigate the existence of solutions of the Poisson-type equations associated with differential second quantization operators as well as operators similar to differential second quantization operators.     

On One Class of Operators Associated with Differential Equations of Fractional Order

We carry out spectral analysis of one class of integral operators associated with fractional order differential equations applicable in mechanics. We establish connection between the eigenvalues of these operators and the zeros of Mittag-Leffler type functions. We give sufficient conditions for complete nonselfadjointness.     

Diffusion Processes Associated with Nonlinear Evolution Equations for Signed Measures

In this paper, we explain how to associate a nonlinear martingale problem with some nonlinear parabolic evolution equations starting at bounded signed measures. Our approach generalizes the classical link made when the initial condition is a probability measure. It consists in giving to each sample-path a signed weight which depends on the initial position. After dealing with the classical McKean-Vlasov equation as an introductory example, we are interested in a viscous scalar conservation law. We prove uniqueness for the corresponding nonlinear martingale problem and then obtain existence thanks to a propagation of chaos result for a system of weakly interacting diffusion processes. Last, we study the behavior of the associated fluctuations and present numerical results which confirm the theoretical rate of convergence.     

Recursion Operators for a Class of Integrable Third-Order Evolution Equations

We consider   u_t = u ^α u_xxx + n ( u ) u_xu_xx + m ( u ) u ³ _x + r ( u ) u_xx + p ( u ) u ² _x + q ( u ) u_x + s ( u )  with  α= 0  and  α= 3  , for those functional forms of   m , n , p , q , r , s   for which the equation is integrable in the sense of an infinite number of Lie-Bäcklund symmetries. Recursion operators which are x - and t -independent that generate these infinite sets of (local) symmetries are obtained for the equations. A combination of potential forms, hodograph transformations, and x -generalized hodograph transformations are applied to the obtained equations.     

Quadratic Control for Stochastic Systems Defined by Evolution Operators and Square Integrable Martingales

The infinite dimensional version of the linear quadratic cost control problem is studied by Curtain and Pritchard [2], Gibson [5] by using Riccati integral equations, instead of differential equations. In the present paper the corresponding stochastic case over a finite horizon is considered. The stochastic perturbations are given by Hilbert valued square integrable martingales and it is shown that the deterministic optimal feedback control is also optimal in the stochastic case. Sufficient conditions are given for the convergence of approximate solutions of optimal control problems.     

Operators Defined on n-Modular Spaces

In this paper we study the operators defined between n-modular spaces. In particular, compact operators are studied and then given some applications to fixed points.     

Pseudodifferential Operators Associated with a Semigroup of Operators

Related to a semigroup of operators on a metric measure space, we define and study pseudodifferential operators (including the setting of Riemannian manifolds, fractals, graphs etc.). Boundedness on L ^p for pseudodifferential operators of order 0 is proved. We mainly focus on symbols belonging to the class $S^{0}_{1,\delta}$ for δ∈[0,1). For the limit class $S^{0}_{1,1}$ , we describe some results by restricting our attention to the case of a sub-Laplacian operator on a Riemannian manifold.     

由发展算子确定的具有控制不等式约束的LQCP的最优反馈控制

研究由发展算子定义的具有控制函数积分不等式约束的线性二次控制问题（LQCP）,借助无约束线性二次控制系统推导出了最优控制的反馈形式。     

有积分算子的非线性发展方程的空间周期分叉解及其稳定性*

本文研究比较一般的有积分算子的非线性发展方程的空间周期分叉解及稳定性问题。首先分别研究分叉解存在的必要条件和充分条件,然后用算子半群方法分析平衡解的稳定性,并讨论了稳定性交换原则。最后研究一个应用例子,对有指数型积分算子的情形得到具体结果。     

Operators Associated with the Ornstein-Uhlenbeck Semigroup

Some of the arguments and techniques developed by the authorsin a previous paper are applied to the study of the boundednessof certain operators associated with the Ornstein–Uhlenbecksemigroup. In particular, a simple proof is given of the weaktype 1 with respect to the Gaussian measure of the Riesz transformsof order 1 and the Littlewood–Paley g-function which thenis extended to show the same property for the Riesz transformsof order 2. For Riesz transforms of higher order boundednessis shown in appropriate spaces close to L¹.     

Exponentially Dichotomous Operators and Exponential Dichotomy of Evolution Equations on the Half-Line

To an evolution family on the half-line of bounded operators on a Banach space X we associate operators I_X and I_Z related to the integral equation and a closed subspace Z of X. We characterize the exponential dichotomy of by the exponential dichotomy and the quasi-exponential dichotomy of the operators X we associate operators I_X and I_Z, respectively.