scholarly journals Error estimates for Gauss-Jacobi quadrature formulae with weights having the whole real line as their support

1980 ◽  
Vol 30 (4) ◽  
pp. 309-314 ◽  
Author(s):  
Radwan Aljarrah

A numerical method for determining the Titchmarsh-Weyl m ( λ ) function for the singular eigenvalue equation – ( py' )' + qy = λwy on [ a ,∞), where a is finite, is presented. The algorithm, based on Weyl’s theory, utilizes a result first used by Atkinson to map a point on the real line onto the Weyl circle in the complex plane. In the limit-point case these circles ‘nest’ and tend to the limit-point m ( λ ). Using Weyl’s result for the diameter of the circles, error estimates for m ( λ ) are obtained. In 1971, W. N. Everitt obtained an extension of an integral inequality of Hardy-Littlewood, namely the help inequality. He showed that the existence of that inequality is determined by the properties of the null set of Im[ λ 2 m ( λ )]. In view of the major difficulties in analysing m ( λ ) even in the rare cases when it is given explicitly, very few examples of the help inequality are known. The computational techniques discussed in this paper have been applied to the problem of finding best constants in these inequalities.


2009 ◽  
Vol 14 (1) ◽  
pp. 127-138 ◽  
Author(s):  
Gennadi Vainikko

The cardinal interpolant of functions on the real line by splines is determined by certain formula free of solving large or infinite systems. We apply this formula to functions given on the interval [0,1] introducing special extensions of functions from [0,1] into the real line which maintains the optimal error estimates. The computation of the parameters determining the interpolant costs O(n log n) operations.


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