RUS  ENG
Полная версия
ЖУРНАЛЫ // Проблемы анализа — Issues of Analysis // Архив

Пробл. анал. Issues Anal., 2025, том 14(32), выпуск 3, страницы 23–43 (Mi pa430)

On removing restrictions in the Bernstein theorem and its modifications

E. G. Kompaneets, V. V. Starkov, E. S. Shmidt

Petrozavodsk State University, 33 Lenina pr., Petrozavodsk 185910, Russia

Аннотация: In 1930, S. N. Bernstein proved the following theorem: Let $f$ and $F$ be complex polynomials such that 1) $\mathrm{deg}\, f \le \mathrm{deg}\, F=n$; 2) $F$ has all its zeros in closure of the disc $\Delta=\{z\in \mathbb{C}\colon |z|<1\}$; 3) $|f(z)| \le |F(z)|$ for $|z|=1$. Then $|f'(z)| \le |F'(z)|$ in $\mathbb{C}\setminus\Delta$. In a huge number of papers that appeared after 1930 and related to this theorem, the restrictions on the geometry of domains and conditions 1) and 2) of the theorem usually remained unchanged. In this article, we consistently remove these restrictions and find out how this will affect the final inequality $|f'(z)| \le |F'(z)|$ of the Bernstein theorem and many of its modifications, generalizations, and consequences.

Ключевые слова: differential inequalities for polynomials, differential operator, $L^p$ inequalities, convex sets.

УДК: 517.53

MSC: 30C10, 30A10

Поступила в редакцию: 20.09.2025
Исправленный вариант: 03.11.2025
Принята в печать: 03.11.2025

Язык публикации: английский

DOI: 10.15393/j3.art.2025.19212



© МИАН, 2026