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Discrete Fourier analysis and Chebyshev polynomials with \(G_{2}\) group. (English) Zbl 1270.41002

Summary: The discrete Fourier analysis on the \(30^\circ\)-\(60^\circ\)-\(90^\circ \) triangle is deduced from the corresponding results on the regular hexagon by considering functions invariant under the group \(G_{2}\), which leads to the definition of four families generalized Chebyshev polynomials. The study of these polynomials leads to a Sturm-Liouville eigenvalue problem that contains two parameters, whose solutions are analogues of the Jacobi polynomials. Under a concept of \(m\)-degree and by introducing a new ordering among monomials, these polynomials are shown to share properties of the ordinary orthogonal polynomials. In particular, their common zeros generate cubature rules of Gauss type.

MSC:

41A05 Interpolation in approximation theory
41A10 Approximation by polynomials