PlanetMath (more info)
 Math for the people, by the people. Sponsor PlanetMath
Encyclopedia | Requests | Forums | Docs | Wiki | Random | RSS  
Login
create new user
name:
pass:
forget your password?
Main Menu
Revision difference : Marty's theorem
Version 3 Version 2
\theoremstyle{theorem}
\newtheorem*{thm}{Theorem}
\begin{thm}[Marty] \begin{thm}[Marty]
A set ${\mathcal{F}}$ of meromorphic functions is a normal family A set ${\mathcal{F}}$ of meromorphic functions is a normal family
on a domain $G \subset {\mathbb{C}}$ if and only if the spherical on a domain $G \subset {\mathbb{C}}$ if and only if the spherical
derivatives are uniformly bounded derivatives are uniformly bounded
on each compact subset of $G$. on each compact subset of $G$.
\end{thm} \end{thm}
Here normal convergence (convergence on compact subsets) is given using the Here normal convergence (convergence on compact subsets) is given using the
spherical metric and not the standard metric of the complex plane. That is if spherical metric and not the standard metric of the complex plane. That is if
$\sigma$ is the spherical metric then we will say $f_n \to f$ normally $\sigma$ is the spherical metric then we will say $f_n \to f$ normally
if $\sigma(f_n(z),f(z))$ converges to 0 uniformly on compact subsets. if $\sigma(f_n(z),f(z))$ converges to 0 uniformly on compact subsets.
A related theorem can be stated. A related theorem can be stated.
\begin{thm} \begin{thm}
If $f_n(z) \to f(z)$ uniformly in the spherical metric on compact subsets of If $f_n(z) \to f(z)$ uniformly in the spherical metric on compact subsets of
$G \subset {\mathbb{C}}$ then $f_n^\sharp(z) \to f^\sharp(z)$ uniformly $G \subset {\mathbb{C}}$ then $f_n^\sharp(z) \to f^\sharp(z)$ uniformly
on compact subsets of $G$. on compact subsets of $G$.
\end{thm} \end{thm}
Here $f^\sharp$ denotes the spherical derivative of $f$. Here $f^\sharp$ denotes the spherical derivative of $f$.
\begin{thebibliography}{9} \begin{thebibliography}{9}
\bibitem{Gamelin:complex} \bibitem{Gamelin:complex}
Theodore~B.\@ Gamelin. Theodore~B.\@ Gamelin.
{\em \PMlinkescapetext{Complex Analysis}}. {\em \PMlinkescapetext{Complex Analysis}}.
Springer-Verlag, New York, New York, 2001. Springer-Verlag, New York, New York, 2001.
\end{thebibliography} \end{thebibliography}