-
Weighted norm inequalities for de Branges-Rovnyak spaces and their applications
- American Journal of Mathematics
- Johns Hopkins University Press
- Volume 132, Number 1, February 2010
- pp. 125-155
- 10.1353/ajm.0.0094
- Article
- Additional Information
- Purchase/rental options available:
Let ${\cal H}(b)$ denote the de Branges--Rovnyak space associated with a
function $b$ in the unit ball of $H^\infty({\Bbb C}_+)$. We study the
boundary behavior of the derivatives of functions in ${\cal H}(b)$ and
obtain weighted norm estimates of the form $\|f^{(n)}\|_{L^2(\mu)} \le
C\|f\|_{{\cal H}(b)}$, where $f \in {\cal H}(b)$ and $\mu$ is a
Carleson-type measure on ${\Bbb C}_+\cup{\Bbb R}$. We provide several
applications of these inequalities. We apply them to obtain embedding
theorems for ${\cal H}(b)$ spaces. These results extend Cohn and
Volberg--Treil embedding theorems for the model (star-invariant) subspaces
which are special classes of de Branges--Rovnyak spaces. We also exploit
the inequalities for the derivatives to study stability of Riesz bases of
reproducing kernels $\{k^b_{\lambda_n}\}$ in ${\cal H}(b)$ under small
perturbations of the points $\lambda_n$.