Marcinkiewicz-Zygmund inequalities and polynomial approximation from scattered data on SO(3).

We consider scattered data approximation problems on SO(3). To this end, we construct a new operator for polynomial approximation on the rotation group. This operator reproduces Wigner-D functions up to a given degree and has uniformly bounded Lp-operator norm for all 1 ? p ? ?. The operator provides a polynomial approximation with the same approximation degree of the best polynomial approximation. Moreover, the operator together with a Markov type inequality for Wigner-D functions enables us to derive scattered data Lp-Marcinkiewicz-Zygmund inequalities for these functions for all 1 ? p ? ?. As a major application of such inequalities, we consider the stability of the weighted least squares approximation problem on SO(3)