%------------------------------------------------------------------------------ % Here please write the date of submission of paper or its revisions: This paper has been submitted for AFA the % on January (the 10^th, 2011) and has been accepted on August (the 10^th, 2011). %------------------------------------------------------------------------------ % \documentclass[12pt, reqno]{amsart} \usepackage{amsmath, amsthm, amscd, amsfonts, amssymb, graphicx, color} \usepackage[bookmarksnumbered, colorlinks, plainpages]{hyperref} \textheight 22.5truecm \textwidth 14.5truecm \setlength{\oddsidemargin}{0.35in}\setlength{\evensidemargin}{0.35in} \setlength{\topmargin}{-.5cm} \newtheorem{theorem}{Theorem}[section] \newtheorem{lemma}[theorem]{Lemma} \newtheorem{proposition}[theorem]{Proposition} \newtheorem{corollary}[theorem]{Corollary} \theoremstyle{definition} \newtheorem{definition}[theorem]{Definition} \newtheorem{example}[theorem]{Example} \newtheorem{exercise}[theorem]{Exercise} \newtheorem{conclusion}[theorem]{Conclusion} \newtheorem{conjecture}[theorem]{Conjecture} \newtheorem{criterion}[theorem]{Criterion} \newtheorem{summary}[theorem]{Summary} \newtheorem{axiom}[theorem]{Axiom} \newtheorem{problem}[theorem]{Problem} \theoremstyle{remark} \newtheorem{remark}[theorem]{Remark} \numberwithin{equation}{section} \input{mathrsfs.sty} \begin{document} \setcounter{page}{59} \noindent\parbox{2.95cm}{\includegraphics*[keepaspectratio=true,scale=0.125]{AFA.jpg}} \noindent\parbox{4.85in}{\hspace{0.1mm}\\[1.5cm]\noindent \qquad Ann. Funct. Anal. 2 (2011), no. 2, 59--74\\ {\footnotesize \qquad \textsc{\textbf{$\mathscr{A}$}nnals of \textbf{$\mathscr{F}$}unctional \textbf{$\mathscr{A}$}nalysis}\\ \qquad ISSN: 2008-8752 (electronic)\\ \qquad URL: \textcolor[rgb]{0.00,0.00,0.99}{www.emis.de/journals/AFA/} }\\[.5in]} \title[$H^{\infty}$ interpolation in weighted Hardy and Bergman norms]{Effective $H^{\infty}$ interpolation constrained by weighted Hardy and Bergman norms} \author[R. Zarouf]{Rachid Zarouf} \address{CMI-LATP, UMR 6632, Universit\'e de Provence, 39, rue Fr\'ed\'eric Joliot-Curie, 13453 Marseille cedex 13, France} \email{\textcolor[rgb]{0.00,0.00,0.84}{rzarouf@cmi.univ-mrs.fr}} \dedicatory{{\rm Communicated by K. Guerlebeck}} \subjclass[2010]{Primary 30E05; Secondary 32A35, 32A36, 46E20, 46J15.} \keywords{Nevanlinna--Pick interpolation, Carleson interpolation, weighted Hardy spaces, weighted Bergman spaces.} \date{Received: 10 January 2011; Accepted: 10 August 2011.} \begin{abstract} Given a finite subset $\sigma$ of the unit disc $\mathbb{D}$ and a holomorphic function $f$ in $\mathbb{D}$ belonging to a class $X$, we are looking for a function $g$ in another class $Y$ which satisfies $g_{\vert\sigma}=f_{\vert\sigma}$ and is of minimal norm in $Y$. More precisely, we consider the interpolation constant $c\left(\sigma,\, X,\, Y\right)=\mbox{sup}{}_{f\in X,\,\parallel f\parallel_{X}\leq1}\mbox{inf}_{g_{\vert\sigma}=f_{\vert\sigma}}\left\Vert g\right\Vert _{Y}.$ When $Y=H^{\infty}$, our interpolation problem includes those of Nevanlinna--Pick and Carath\'eodory--Schur. If $X$ is a Hilbert space belonging to the families of weighted Hardy and Bergman spaces, we obtain a sharp upper bound for the constant $c\left(\sigma,\, X,\, H^{\infty}\right)$ in terms of $n=\mbox{card}\,\sigma$ and $r=\mbox{max}{}_{\lambda\in\sigma}\left|\lambda\right|<1$. If $X$ is a general Hardy--Sobolev space or a general weighted Bergman space (not necessarily of Hilbert type), we also establish upper and lower bounds for $c\left(\sigma,\, X,\, H^{\infty}\right)$ but with some gaps between these bounds. This problem of constrained interpolation is partially motivated by applications in matrix analysis and in operator theory. \end{abstract} \maketitle \vspace{1in} \end{document} .