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MATHEMATICS
Complement to the Hölder inequality for multiple integrals. I
B. F. Ivanov St Petersburg State University of Industrial Technologies and Design, 18, ul. Bolshaya Morskaya, St Petersburg, 191186, Russian Federation
Abstract:
This article is the first part of the work, the main result of which is the statement that if for functions $\gamma_1 \in L^{p_1} (\mathbb{R}^n), \ldots, \gamma_m \in L^{p_m}(\mathbb{R}^n)$, where
$m \geqslant 2$ and the numbers
$p_1, \ldots, p_m \in (1, +\infty]$ are such that
$1/p_1 + \ldots + 1/p_m<1$, a non-resonant condition is met (the concept introduced by the author for functions from
$L^{p} (\mathbb{R}^n), p \in (1, +\infty])$, then $\sup_{a,b\in \mathbb{R}^n}|\int\limits_{[a,b]} \prod_{k=1}^m[\gamma_k(\tau) + \Delta\gamma_k(\tau)]d\tau|\leqslant C\prod_{k=1}^m||\gamma_k + \Delta\gamma_k||_{L_{h_k}^{p_k}(\mathbb{R}^n)}$, where
$[a, b]$ is an
$n$-dimensional parallelepiped, the constant
$C > 0$ does not depend on functions
$\Delta\gamma_k\in L_{h_k}^{p_k}(\mathbb{R}^n)$, and $L_{h_k}^{p_k}(\mathbb{R}^n) \in L^{p_k}(\mathbb{R}^n), 1\leqslant k\leqslant m$, are specially constructed normalized spaces. In the article, for any spaces
$L^p(\mathbb{R}^n)$,
$p_0$,
$p \in (1,+\infty]$ and any function
$\gamma \in L^{p_0} (\mathbb{R}^n)$ the concept of a set of resonant points of a function
$\gamma$ with respect to the
$L^p(\mathbb{R}^n)$ is introduced. This set is a subset of
${ \mathbb{R}^1 \cup {\infty}}^n$ for any trigonometric polynomial of n variables with respect to any
$L^p(\mathbb{R}^n)$ represents the spectrum of the polynomial in question. Theorems are written on the representation of each function
$\gamma \in L^{p_0}(\mathbb{R}^n)$ with a nonempty resonant set as the sum of two functions such that the first of them belongs to the
$L^{p_0}(\mathbb{R}^n) \cap L^q(\mathbb{R}^n)$,
$1/p + 1/q = 1$, and the carrier of the Fourier transform of the second is centered in the neighborhood of the resonant set.
Keywords:
the Holder inequality.
UDC:
517
MSC: 26D15 Received: 20.10.2021
Revised: 30.11.2021
Accepted: 02.12.2021
DOI:
10.21638/spbu01.2022.207