Algebraic Properties of Multilevel Interpolations for the Nikishin System.

We discuss the algebraic properties of a pair of dual multilevel interpolation problems for the Nikishin system. In particular, we will focus on recurrence relations and the Christoffel–Darboux formula. As a consequence, we obtain well-known formulas for biorthogonal polynomials with an iterated Cauchy kernel, which recently arose in the study of multimatrix models.