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JOURNALS // Zapiski Nauchnykh Seminarov POMI // Archive

Zap. Nauchn. Sem. POMI, 2005 Volume 323, Pages 24–33 (Mi znsl377)

This article is cited in 2 papers

On the region of values of the system $\{f(z_1),\dots,f(z_n)\}$ in the class of typically real functions. II

E. G. Goluzina

St. Petersburg Department of V. A. Steklov Institute of Mathematics, Russian Academy of Sciences

Abstract: The paper studies the region $D_{m,1}(T)$ of values of the system $\{f(z_1),f(z_2),\dots,f(z_m),f(r)\}$, $m\ge1$, where $z_j$ ($j=1,2,\dots,m$) are arbitrary fixed points of the disk $U=\{z:|z|<1\}$ with $\operatorname{Im}z_j\ne0$ ($j=1,2,\ldots,m$), and $r$, $0<r<1$, is fixed, on the class $T$ of functions $f(z)=z+a_2z^2+\cdots$ regular in the disk $U$ and satisfying in the latter the condition $\operatorname{Im}f(z)\operatorname{Im}z>0$ for $\operatorname{Im}z\ne0$. An algebraic characterization of the set $D_{m,1}(T)$ in terms of nonnegative Hermitian forms is given, and all the boundary functions are described. As an implication, the region of values of $f(z_m)$ in the subclass of functions from the class $T$ with prescribed values $f(z_k)$ ($k=1,2,\dots,m-1$) and $f(r)$ is determined.

UDC: 517.54

Received: 13.06.2005


 English version:
Journal of Mathematical Sciences (New York), 2006, 137:3, 4774–4779

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