arXiv subjects

Niklas Wikman

Publications and source records attributed to Niklas Wikman.

3 recordsLinked to original sources

arXiv2020

On the exact value of the norm of the Hilbert matrix operator on weighted Bergman spaces

In this article, the open problem of finding the exact value of the norm of the Hilbert matrix operator on weighted Bergman spaces $A^p_\alpha$ is adressed. The norm was conjectured to be $\frac{\pi}{\sin \frac{(2+\alpha)\pi}{p}}$ by Karapetrovi\'{c}. We obtain a complete solution to the conjecture for $\alpha \ge 0$ and $2+\alpha+\sqrt{\alpha^2+\frac{7}{2}\alpha+3} \le p < 2(2+\alpha)$ and a partial solution for $2+2\alpha < p < 2+\alpha+\sqrt{\alpha^2+\frac{7}{2}\alpha+3}.$ Moreover, we also show that the conjecture is valid for small values of $\alpha$ when $2+2\alpha < p \le 3+2\alpha.$ Finally, the case $\alpha = 1$ is considered.

math.FA↗

arXiv2018

Norm estimates of weighted composition operators pertaining to the Hilbert Matrix

Very recently, Bo\v{z}in and Karapetrovi\'c solved a conjecture by proving that the norm of the Hilbert matrix operator $\mathcal{H}$ on the Bergman space $A^p$ is equal to $\frac{\pi}{\sin(\frac{2\pi}{p})}$ for $2 < p < 4.$ In this article we present a partly new and simplified proof of this result. Moreover, we calculate the exact value of the norm of $\mathcal{H}$ defined on the Korenblum spaces $H^\infty_\alpha$ for $0 < \alpha \le 2/3$ and an upper bound for the norm on the scale $2/3 < \alpha < 1$.

math.FA↗

arXiv2018

Generalized Volterra operators mapping between Banach spaces of analytic functions

We characterize boundedness and compactness of the classical Volterra operator $T_g \colon H_{v_{\alpha}}^{\infty} \to H^{\infty}$ induced by a univalent function $g$ for standard weights $v_{\alpha}$ with $0 \leq \alpha < 1$, partly answering an open problem posed by A. Anderson, M. Jovovic and W. Smith. We also study boundedness, compactness and weak compactness of the generalized Volterra operator $T_g^{\varphi}$ mapping between Banach spaces of analytic functions on the unit disc satisfying certain general conditions.

math.FA↗