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JOURNALS // Izvestiya Rossiiskoi Akademii Nauk. Seriya Matematicheskaya // Archive

Izv. RAN. Ser. Mat., 2010 Volume 74, Issue 4, Pages 63–74 (Mi im4021)

On the massiveness of exceptional sets of the maximum modulus principle

V. I. Danchenko

Vladimir State University

Abstract: We consider the sets $E_{\nu}(f)=\{z\colon |f(z)|\geqslant \nu\}$ for $\nu>\nu_0(f):=\limsup_{z\to\partial D}|f(z)|$ in the disc $D=\{z\colon |z|<1\}$, where $f(z)$, $z=x+iy$, are complex-valued functions defined on $D$ and having certain smoothness properties with respect to the real variables $x$ and $y$. We obtain estimates for some metric properties of the sets $E_{\nu}(f)$. For example, we prove that, if $\Delta f\in L_1(D)$, then the hyperbolic area of the set $E_\nu(f)$ cannot grow more rapidly than $\nu^{-1-o(1)}$ as $\nu\to 0$, where $o(1)$ is positive, and, if $f_{\bar{z}}\in L_2(D)$, then this area cannot grow more rapidly than $\nu^{-2-o(1)}$. The orders of these estimates with respect to $\nu$ are sharp.

Keywords: hyperbolic distance and area, capacity and potential, polyanalytic function, maximum modulus principle, Green's formulae.

UDC: 517.544.5+517.544.45

MSC: Primary 30C85; Secondary 31A15

Received: 18.09.2008

DOI: 10.4213/im4021


 English version:
Izvestiya: Mathematics, 2010, 74:4, 723–734

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© Steklov Math. Inst. of RAS, 2024