Abstract
We study the problem of characterizing the best approximation by polynomials on the unit ball in terms of the smoothness of the function being approximated,similar to what we did on the unit sphere in Chap. 4. There is, however, an essential difference between approximations on the unit ball and those on the unit sphere, which arises from the simple fact that the ball is a domain with boundary, whereas the sphere has no boundary.
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Dai, F., Xu, Y. (2013). Polynomial Approximation on the Unit Ball. In: Approximation Theory and Harmonic Analysis on Spheres and Balls. Springer Monographs in Mathematics. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-6660-4_12
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DOI: https://doi.org/10.1007/978-1-4614-6660-4_12
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