Unbounded Multipliers of Complete Pick Spaces

The Structure of Inner Multipliers on Spaces with Complete Nevanlinna Pick Kernels

Let k be the reporducing kernel for a Hilbert space H(k) of nanlytic functions on Bd, the open unit ball in C, d ≥ 1. k is called a complete NP kernel, if k0 ≡ 1 and if 1 − 1/kλ(z) is positive definite on Bd × Bd. Let D be a separable Hilbert space, and consider H(k) ⊗ D ∼= H(k,D), and think of it as a space of D-valued H(k)-functions. A theorem of McCullough and Trent, [10], partially extends ...

Spaces of Dirichlet series with the complete Pick property

We consider reproducing kernel Hilbert spaces of Dirichlet series with kernels of the form k(s, u) = ∑ ann −s−ū, and characterize when such a space is a complete Pick space. We then discuss what it means for two reproducing kernel Hilbert spaces to be “the same”, and introduce a notion of weak isomorphism. Many of the spaces we consider turn out to be weakly isomorphic as reproducing kernel Hil...

Complete Multipliers

We investigate whether the completeness of a complete orthonormal sequence for L2(IT, 77) is preserved if the sequence is perturbed by multiplying a portion of it by a fixed function. For the particular sequence i(277)-1/2emxi we show that given any xb £ L°°(-77, 77), except lb = 0 a.e., there is a nontrivial portion of Í (2rr)-^ einx\ which will maintain completeness under this perturbation. W...

Multipliers of generalized frames in Hilbert spaces

Complete Nevanlinna-Pick Kernels

We give a new treatment of Quiggin’s and McCullough’s characterization of complete Nevanlinna-Pick kernels. We show that a kernel has the matrix-valued NevanlinnaPick property if and only if it has the vector-valued Nevanlinna-Pick property. We give a representation of all complete Nevanlinna-Pick kernels, and show that they are all restrictions of a universal complete Nevanlinna-Pick kernel.