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On some characteristics of the growth of subharmonic functions
A. V. Bratishchev,
Yu. F. Korobeinik
Abstract:
The connection between the growth of a function which is subharmonic in the plane and the growth of its associated Riesz measure is studied. The principal result (actually obtained in a more general form) is:
Theorem. {\it Suppose that the function
$h(r)$ is differentiable on
$(0,\infty)$, with
$h'(x)>0$ and
$$
\lim_{x\to\infty}\frac{\ln x}{h(x)}=0,\qquad\lim_{x\to\infty}\frac{x\cdot h'(x)}{h(x)}=0.
$$
Define
$$
\alpha_h(r)=\max_{1<\theta<\infty}\frac{\ln\theta}{h(\theta\cdot r)},\qquad\Delta_h=\varliminf_{r\to\infty}rh'(r)\alpha_h(r).
$$
Suppose further that
$\varphi(u)$ is a function which is subharmonic in
$\mathbf R^2$, is of zero order, and has associated measure
$\mu$. Then
\begin{gather*}
\Delta_h\varlimsup_{r\to\infty}\frac{\mu(r)}{rh'(r)}\leqslant\varlimsup_{r\to\infty}\frac{M_\varphi(r)}{h(r)}
\leqslant\varlimsup_{r\to\infty}\frac{\mu(r)}{rh'(r)},\\
\varliminf_{r\to\infty}\frac{M_\varphi(r)}{h(r)}\geqslant\varliminf_{r\to\infty}\frac{\mu(r)}{rh'(r)},
\end{gather*}
where
$$
\mu(r)=\mu(|z|\leqslant r),\qquadM_\varphi(r)\max\bigl\{0,\{\varphi(u):|u|=r\}\bigr\}.
$$
If, in addition,
$x\cdot h'(x)/h(x)$ is nonincreasing, then
$\Delta_h\geqslant1/e$.}
Bibliography: 12 titles.
UDC:
517.5
MSC: 31A05,
30D15 Received: 05.05.1977