
The authors abstract is accurate: We study Chebyshev type quadrature formulas of degree \(n\) with respect to a weight function on \(\langle - 1,+1 \rangle\), i.e. formulas \[ {1 \over {\int_{-1}^{+1} w(t)dt}}\cdot \int_{-1}^{+1} f(t) w(t) dt={1\over N} \sum_{i=1}^ N f(x_ i)+ R(f) \] with nodes \(x_ i\in \langle -1,+1\rangle\) such that \(R(f)=0\) for every polynomial of degree \(\leq n\). It is known that for a Jacobi weight function \(w(t)= (1-t)^ \alpha (1+t)^ \beta\) the number of nodes has to satisfy the inequality \(N\geq K_ 1 n^{2+2\max(\alpha, \beta)}\) for some absolute constant \(K_ 1>0\). In this paper it is shown that for an ultraspherical weight function \(w(t)= (1-t^ 2)^ \alpha\) with \(\alpha\geq 0\), this lower bound is of the right order i.e. there exists a Chebyshev type quadrature formula of degree \(n\) with \(N\leq K_ 2 n^{2+2\alpha}\) nodes. Our method of proof is based on a method of S. N. Bernstein who obtained the result in case \(\alpha=0\). In general this method gives a large number of multiple nodes. It is also shown that the nodes can be chosen to be distinct.
Chebyshev type quadrature formulas, Mathematics(all), Numerical integration, ultraspherical weight function, Approximate quadratures, Jacobi weight function
Chebyshev type quadrature formulas, Mathematics(all), Numerical integration, ultraspherical weight function, Approximate quadratures, Jacobi weight function
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