Density Questions for the Truncated Matrix Moment Problem
Antonio J. Durán, Pedro Lopez-Rodriguez · Canadian Journal of Mathematics · 1997
Abstract For a truncated matrix moment problem, we describe in detail the set of positive definite matrices of measures μ in V2n (this is the set of solutions of the problem of degree 2n) for which the polynomials up to degree n are dense in the corresponding space L2(μ). These matrices of measures are exactly the extremal measures of the set Vn.