Zapiski Nauchnykh Seminarov POMI
RUS  ENG    JOURNALS   PEOPLE   ORGANISATIONS   CONFERENCES   SEMINARS   VIDEO LIBRARY   PACKAGE AMSBIB  
General information
Latest issue
Archive
Impact factor

Search papers
Search references

RSS
Latest issue
Current issues
Archive issues
What is RSS



Zap. Nauchn. Sem. POMI:
Year:
Volume:
Issue:
Page:
Find






Personal entry:
Login:
Password:
Save password
Enter
Forgotten password?
Register


Zapiski Nauchnykh Seminarov POMI, 1992, Volume 201, Pages 157–163 (Mi znsl5110)  

This article is cited in 4 scientific papers (total in 4 papers)

Boundary distortions and change of module under extension of a doubly connected domain

A. Yu. Solynin
Full-text PDF (346 kB) Citations (4)
Abstract: Let $\mathcal{F}(p,r)$ denote the class of univalent analytic functions $f(z)$ in the domain $\mathcal{K}(\rho)=\{z: \rho<|z|<1\}$, satisfying $|f(z)|=1$ for $|z|=1$ and $r<|f(z)|<1$ for $z\in\mathcal{K}(\rho)$. Let $f(z;\rho,r)$ map $\mathcal{K}(\rho)$ onto the domain $\mathcal{K}(r)\setminus[r,s]$ and let $f(z;\rho,r)\in\mathcal{F}(\rho,r)$.
THEOREM 2. Let $f(z)\in\mathcal{F}(\rho,r)$, $f(z)\ne e^{i\alpha}f(z;\rho,r)$, $\alpha\in\mathbb{R}$, and $\Phi(t)$ be a strictly convex monotone function of $t>0$. Then
$$ \int_0^{2\pi}\Phi(|f'(e^{i\theta})|)d\theta<\int_0^{2\pi}\Phi(|f'(e^{i\theta};\rho,r)|)d\,\theta. $$
The proof of this theorem is based on the Golusin–Komatu equation.
If $E$ is a continuum in the disk $U_R=\{z: |z|<R\}$, then $M(R,E)$ denotes the conformal module of the doubly connected component of $U_R\setminus E$; let $\varepsilon(m)=\{E: \overline{U}_r\subset E\subset U_1,\ M(1, E)=m^{-1}\}$.
PROBLEM. Find the maximum of $M(R, E)$, $R>1$, and the minimum of cap $E$ over all $E$ in $\varepsilon(m)$. This problem was posed by V. V. Koževnikov in a lecture to the seminare on geometric function theory at the Kuban university in 1980, and by D. Gaier (see [2]). The solution of this problem is given by the following theorem.
THEOREM 3. Let $E^*=\overline{U}_m\cup[m, s]$. If $R>1; E, E^*\in\varepsilon(m)$ and $E\ne e^{i\alpha}E^*$, $\alpha\in\mathbb{R}$, then
$$ M(R, E)<M(R,E^*),\quad \mathrm{cap}\,E^*<\mathrm{cap}\,E. $$
A similar statement is also proved for continue lying in the half-plane.
ADDENDUM. When the paper was ready for publication, the author obtained a letter from R. Laugesen with the information that he had also proved Theorem 3 by a different method based on results of A. Baernstein. II on potential theory.
English version:
Journal of Mathematical Sciences, 1996, Volume 78, Issue 2, Pages 218–222
DOI: https://doi.org/10.1007/BF02366036
Bibliographic databases:
Document Type: Article
UDC: 517.54
Language: Russian
Citation: A. Yu. Solynin, “Boundary distortions and change of module under extension of a doubly connected domain”, Investigations on linear operators and function theory. Part 20, Zap. Nauchn. Sem. POMI, 201, Nauka, St. Petersburg, 1992, 157–163; J. Math. Sci., 78:2 (1996), 218–222
Citation in format AMSBIB
\Bibitem{Sol92}
\by A.~Yu.~Solynin
\paper Boundary distortions and change of module under extension of a doubly connected domain
\inbook Investigations on linear operators and function theory. Part~20
\serial Zap. Nauchn. Sem. POMI
\yr 1992
\vol 201
\pages 157--163
\publ Nauka
\publaddr St.~Petersburg
\mathnet{http://mi.mathnet.ru/znsl5110}
\mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=1172763}
\zmath{https://zbmath.org/?q=an:0839.30019|0804.30020}
\transl
\jour J. Math. Sci.
\yr 1996
\vol 78
\issue 2
\pages 218--222
\crossref{https://doi.org/10.1007/BF02366036}
Linking options:
  • https://www.mathnet.ru/eng/znsl5110
  • https://www.mathnet.ru/eng/znsl/v201/p157
  • This publication is cited in the following 4 articles:
    Citing articles in Google Scholar: Russian citations, English citations
    Related articles in Google Scholar: Russian articles, English articles
    Записки научных семинаров ПОМИ
    Statistics & downloads:
    Abstract page:166
    Full-text PDF :44
     
      Contact us:
     Terms of Use  Registration to the website  Logotypes © Steklov Mathematical Institute RAS, 2024