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ЖУРНАЛЫ // Уфимский математический журнал // Архив

Уфимск. матем. журн., 2017, том 9, выпуск 4, страницы 137–146 (Mi ufa410)

Эта публикация цитируется в 6 статьях

Minimum modulus of lacunary power series and $h$-measure of exceptional sets

T. M. Saloa, O. B. Skaskivb

a Institute of Applied Mathematics and Fundamental Sciences, National University "Lvivs’ka Polytehnika", Stepan Bandera str. 12, 79013, Lviv, Ukraine
b Department of Mechanics and Mathematics, Ivan Franko National University of L’viv, Universytetska str. 1, 79000, Lviv, Ukraine

Аннотация: We consider some generalizations of Fenton theorem for the entire functions represented by lacunary power series. Let $f(z)=\sum_{k=0}^{+\infty}f_kz^{n_k}$, where $(n_k)$ is a strictly increasing sequence of non-negative integers. We denote by
\begin{align*} &M_f(r)=\max\{|f(z)|\colon |z|=r\}, \\ &m_f(r)=\min\{|f(z)|\colon |z|=r\}, \\ & \mu_f(r)=\max\{|f_k|r^{n_k}\colon k\geq 0\} \end{align*}
the maximum modulus, the minimum modulus and the maximum term of $f,$ respectively. Let $h(r)$ be a positive continuous function increasing to infinity on $[1,+\infty)$ with a non-decreasing derivative. For a measurable set $E\subset [1,+\infty)$ we introduce $h-\mathrm{meas}\,(E)=\int_{E}\frac{dh(r)}{r}.$ In this paper we establish conditions guaranteeing that the relations
$$ M_f(r)=(1+o(1)) m_f(r),\quad M_f(r)=(1+o(1))\mu_f(r) $$
are true as $r\to+\infty$ outside some exceptional set $E$ such that $h-\mathrm{meas}\,(E)<+\infty$. For some subclasses we obtain necessary and sufficient conditions. We also provide similar results for entire Dirichlet series.

Ключевые слова: lacunary power series, minimum modulus, maximum modulus, maximal term, entire Dirichlet series, exceptional set, $h$-measure.

УДК: 517.576

MSC: 30B50

Поступила в редакцию: 22.07.2016

Язык публикации: английский


 Англоязычная версия: Ufa Mathematical Journal, 2017, 9:4, 135–144

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