On the pointwise limits of bivariate Lagrange projectors

  title={On the pointwise limits of bivariate Lagrange projectors},
  author={Carl de Boor and Boris Shekhtman},
A linear algebra proof is given of the fact that the nullspace of a finite-rank linear projector, on polynomials in two complex variables, is an ideal if and only if the projector is the bounded pointwise limit of Lagrange projectors, i.e., projectors whose nullspace is a radical ideal, i.e., the set of all polynomials that vanish on a certain given finite set. A characterization of such projectors is also given in the real case. More generally, a characterization is given of those finite-rank… CONTINUE READING