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Proceedings of the American Mathematical Society
Proceedings of the American Mathematical Society
ISSN 1088-6826(e) ISSN 0002-9939(p)

     

The Nevanlinna counting functions for Rudin's orthogonal functions

Author(s): Takahiko Nakazi
Journal: Proc. Amer. Math. Soc. 131 (2003), 1267-1271.
MSC (2000): Primary 30D50
Posted: September 5, 2002
MathSciNet review: 1948119
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Abstract | References | Similar articles | Additional information

Abstract: $H^\infty$ and $H^2$ denote the Hardy spaces on the open unit disc $D$. Let $\phi$ be a function in $H^\infty$ and $\Vert\phi\Vert _\infty = 1$. If $\phi$ is an inner function and $\phi(0) = 0$, then $\{\phi^n~;~n = 0,1,2,\cdots \}$ is orthogonal in $H^2$. W.Rudin asked if the converse is true and C. Sundberg and C. Bishop showed that the converse is not true. Therefore there exists a function $\phi$ such that $\phi$ is not an inner function and $\{\phi^n\}$ is orthogonal in $H^2$. In this paper, the following is shown: $\{\phi^n\}$ is orthogonal in $H^2$ if and only if there exists a unique probability measure $\nu_0$ on [0,1] with $1 \in $ supp $\nu_0$ such that $N_\phi(z) = {\int^1_{\vert z\vert}} \log \frac{r}{\vert z\vert} d\nu_0(r)$ for nearly all $z$ in $D$ where $N_\phi$ is the Nevanlinna counting function of $\phi$. If $\phi$ is an inner function, then $\nu_0$ is a Dirac measure at $r = 1$.


References:

1.
C. Bishop, Orthogonal functions in $H^\infty$, preprint
2.
P. S. Bourdon, Rudin's orthogonality problem and the Nevanlinna counting function, Proc. Amer. Math. Soc. 125(1997), 1187-1192. MR 98b:30034
3.
J. A. Cima, B. Korenblum and M. Stessin, On Rudin's orthogonality and independence problem, preprint
4.
W. Rudin, Real and Complex Analysis, Third Edition, McGraw-Hill, Inc. MR 88k:00002
5.
W. Rudin, A generalization of a theorem of Frostman, Math. Scand. 21(1967), 136-143. MR 38:3463
6.
J. H. Shapiro, Composition Operators and Classical Function Theory, Springer-Verlag. MR 94k:47049
7.
A. L. Shields, Weighted shift operators and analytic function theory, Math. Surveys, Amer. Math. Soc. 13, 49-128. MR 50:14341
8.
C. Sundberg, Measures induced by analytic functions and a problem of Walter Rudin, preprint

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Additional Information:

Takahiko Nakazi
Affiliation: Department of Mathematics, Hokkaido University, Sapporo 060-0810, Japan
Email: nakazi@math.sci.hokudai.ac.jp

DOI: 10.1090/S0002-9939-02-06671-6
PII: S 0002-9939(02)06671-6
Received by editor(s): December 22, 2000
Received by editor(s) in revised form: December 6, 2001
Posted: September 5, 2002
Additional Notes: This research was partially supported by Grant-in-Aid for Scientific Research, Ministry of Education
Communicated by: Juha M. Heinonen
Copyright of article: Copyright 2002, American Mathematical Society




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