scholarly journals Design of accurate formulas for approximating functions in weighted Hardy spaces by discrete energy minimization

2018 ◽  
Vol 39 (4) ◽  
pp. 1957-1984 ◽  
Author(s):  
Ken’ichiro Tanaka ◽  
Masaaki Sugihara
Keyword(s):  
Hardy Spaces ◽  
Weight Functions ◽  
Approximation Formula ◽  
Optimal Sampling ◽  
Weighted Hardy Spaces ◽  
Sinc Approximation ◽  
Discrete Energy ◽  
Decay Properties ◽  
Sampling Points ◽  
Approximation Formulas

Abstract We propose a simple and effective method for designing approximation formulas for weighted analytic functions. We consider spaces of such functions according to weight functions expressing the decay properties of the functions. Then we adopt the minimum worst error of the $n$-point approximation formulas in each space for characterizing the optimal sampling points for the approximation. In order to obtain approximately optimal sampling points we consider minimization of a discrete energy related to the minimum worst error. Consequently, we obtain an approximation formula and its theoretical error estimate in each space. In addition, from some numerical experiments, we observe that the formula generated by the proposed method outperforms the corresponding formula derived with sinc approximation, which is near optimal in each space.

scholarly journals Toeplitz operators with PQC symbols on weighted Hardy spaces

1991 ◽  
Vol 97 (1) ◽  
pp. 194-214 ◽  
Author(s):  
Albrecht Böttcher ◽  
Ilya M Spitkovsky
Keyword(s):  
Hardy Spaces ◽  
Toeplitz Operators ◽  
Weighted Hardy Spaces

scholarly journals Study on divergence approximation formula for pressure calculation in particle method

2018 ◽  
Vol 10 (4) ◽  
pp. 159-169
Author(s):  
Zhu Yue ◽  
Jiang Shengyao ◽  
Yang Xingtuan ◽  
Duan Riqiang
Keyword(s):  
Pressure Oscillation ◽  
Particle Method ◽  
Free Surface Flows ◽  
Implicit Method ◽  
Approximation Formula ◽  
Pressure Poisson Equation ◽  
Pressure Calculation ◽  
Approximation Formulas ◽  
Moving Particle ◽  
Dam Breaking

The moving particle semi-implicit method is a meshless particle method for incompressible fluid and has proven useful in a wide variety of engineering applications of free-surface flows. Despite its wide applicability, the moving particle semi-implicit method has the defects of spurious unphysical pressure oscillation. Three various divergence approximation formulas, including basic divergence approximation formula, difference divergence approximation formula, and symmetric divergence approximation formula are proposed in this paper. The proposed three divergence approximation formulas are then applied for discretization of source term in pressure Poisson equation. Two numerical tests, including hydrostatic pressure problem and dam-breaking problem, are carried out to assess the performance of different formulas in enhancing and stabilizing the pressure calculation. The results demonstrate that the pressure calculated by basic divergence approximation formula and difference divergence approximation formula fluctuates severely. However, application of symmetric divergence approximation formula can result in a more accurate and stabilized pressure.

scholarly journals An Efficient Compact Difference Method for Temporal Fractional Subdiffusion Equations

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Lei Ren ◽  
Lei Liu
Keyword(s):  
Finite Difference ◽  
Fourth Order ◽  
Difference Method ◽  
Second Order ◽  
Finite Difference Approximation ◽  
Difference Approximation ◽  
Approximation Formula ◽  
Discrete Energy ◽  
Compact Finite Difference ◽  
Second Order In Time

In this paper, a high-order compact finite difference method is proposed for a class of temporal fractional subdiffusion equation. A numerical scheme for the equation has been derived to obtain 2-α in time and fourth-order in space. We improve the results by constructing a compact scheme of second-order in time while keeping fourth-order in space. Based on the L2-1σ approximation formula and a fourth-order compact finite difference approximation, the stability of the constructed scheme and its convergence of second-order in time and fourth-order in space are rigorously proved using a discrete energy analysis method. Applications using two model problems demonstrate the theoretical results.

scholarly journals WEIGHTED HARDY SPACES ASSOCIATED WITH OPERATORS SATISFYING REINFORCED OFF-DIAGONAL ESTIMATES

2013 ◽  
Vol 17 (4) ◽  
pp. 1127-1166 ◽  
Author(s):  
The Anh Bui ◽  
Jun Cao ◽  
Luong Dang Ky ◽  
Dachun Yang ◽  
Sibei Yang
Keyword(s):  
Hardy Spaces ◽  
Weighted Hardy Spaces

scholarly journals Spatial Numerical Range of Operators on Weighted Hardy Spaces

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Abdolaziz Abdollahi ◽  
Mohammad Taghi Heydari
Keyword(s):  
Hardy Spaces ◽  
Finite Rank ◽  
Numerical Range ◽  
Compact Operators ◽  
Weighted Hardy Spaces ◽  
Finite Rank Operators

We consider the spatial numerical range of operators on weighted Hardy spaces and give conditions for closedness of numerical range of compact operators. We also prove that the spatial numerical range of finite rank operators on weighted Hardy spaces is star shaped; though, in general, it does not need to be convex.

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