|
Necessary Conditions for the Weak Generalized Localization of Fourier Series with “Lacunary Sequence of Partial Sums”
O. V. Lifantseva Moscow State Region University
Abstract:
It has been established that, on the subsets $\mathbb{T}^N=[-\pi,\pi]^N$ describing a cross $W$ composed of $N$-dimensional blocks, $W_{x_sx_t}=\Omega_{x_sx_t}\times [-\pi,\pi]^{N-2}$ ($\Omega_{x_sx_t}$ is an open subset of $[-\pi,\pi]^2$) in the classes $L_p(\mathbb{T}^N)$, $p>1$, a weak generalized localization holds, for $N\ge3$, almost everywhere for multiple trigonometric Fourier series when to the rectangular partial sums $S_n(x;f)$ ($x\in\mathbb{T}^N$, $f\in L_p$) of these series corresponds the number $n=(n_1,\dots,n_N)\in\mathbb Z_{+}^{N}$ some components $n_j$ of which are elements of lacunary sequences. In the present paper, we prove a number of statements showing that the structural and geometric characteristics of such subsets are sharp in the sense of the numbers (generating $W$) of the $N$-dimensional blocks $W_{x_sx_t}$ as well as of the structure and geometry of $W_{x_sx_t}$. In particular, it is proved that it is impossible to take an arbitrary measurable two-dimensional set or an open three-dimensional set as the base of the block.
Keywords:
multiple trigonometric Fourier series, $n$-block, lacunary sequence, weak generalized localization, measurable set, Euclidean space, rectangular partial sum.
Received: 23.11.2007 Revised: 17.03.2009
Citation:
O. V. Lifantseva, “Necessary Conditions for the Weak Generalized Localization of Fourier Series with “Lacunary Sequence of Partial Sums””, Mat. Zametki, 86:3 (2009), 408–420; Math. Notes, 86:3 (2009), 373–384
Linking options:
https://www.mathnet.ru/eng/mzm8501https://doi.org/10.4213/mzm8501 https://www.mathnet.ru/eng/mzm/v86/i3/p408
|
|