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Maximum curves and isolated points of entire functions

Author: T. F. Tyler
Journal: Proc. Amer. Math. Soc. 128 (2000), 2561-2568
MSC (2000): Primary 30C80
Published electronically: February 29, 2000
MathSciNet review: 1662226
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Given $M(r,f)=\max_{\vert{z}\vert=r}\left( \vert{f(z)}\vert\right)$ , curves belonging to the set of points $\mathcal{M}=\left\{ z:\vert{f(z)}\vert=M(\vert{z}\vert,f)\right\}$ were defined by Hardy to be maximum curves. Clunie asked the question as to whether the set $\mathcal{ M}$ could also contain isolated points. This paper shows that maximum curves consist of analytic arcs and determines a necessary condition for such curves to intersect. Given two entire functions $f_1(z)$ and $f_2(z)$, if the maximum curve of $f_1(z)$ is the real axis, conditions are found so that the real axis is also a maximum curve for the product function $f_1(z)f_2(z)$. By means of these results an entire function of infinite order is constructed for which the set $\mathcal{M}$ has an infinite number of isolated points. A polynomial is also constructed with an isolated point.

References [Enhancements On Off] (What's this?)

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Additional Information

T. F. Tyler
Affiliation: University of Greenwich, 30, Park Row, Greenwich, London SE10 9LS, United Kingdom

Keywords: Maximum curves, isolated points, analytic functions
Received by editor(s): June 15, 1998
Received by editor(s) in revised form: October 5, 1998
Published electronically: February 29, 2000
Communicated by: Albert Baernstein II
Article copyright: © Copyright 2000 American Mathematical Society

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