Stability Analysis of Grünwald Interpolation Operators on Chebyshev Nodes

Abstract: In 1941, G. Grünwald proved the convergence of a sequence of operators constructed using classical Lagrange interpolation at Chebyshev nodes. In this work, we establish a perturbed version of Grünwald's result, thereby extending the class of admissible nodal points. Specifically, we provide sufficient conditions for convergence when the interpolation nodes are of the form {cos eta_k} for k = 1, ..., n, where {eta_k} is a general sequence. We refer to these operators as Grünwald operators. In particular, we prove a convergence result when {eta_k} is equidistant and uniformly distributed. We establish a Voronovskaja-type estimate for the convergence of these operators and derive quantitative results involving the first and second moduli of smoothness.