Pointwise universal trigonometric series


Autoria(s): Shkarin, Stanislav
Data(s)

15/12/2009

Resumo

A series $S_a=\sum\limits_{n=-\infty}^\infty a_nz^n$ is called a {\it pointwise universal trigonometric series} if for any $f\in C(\T)$, there exists a strictly increasing sequence $\{n_k\}_{k\in\N}$ of positive integers such that $\sum\limits_{j=-n_k}^{n_k} a_jz^j$ converges to $f(z)$ pointwise on $\T$. We find growth conditions on coefficients allowing and forbidding the existence of a pointwise universal trigonometric series. For instance, if $|a_n|=O(\e^{\,|n|\ln^{-1-\epsilon}\!|n|})$ as $|n|\to\infty$ for some $\epsilon>0$, then the series $S_a$ can not be pointwise universal. On the other hand, there exists a pointwise universal trigonometric series $S_a$ with $|a_n|=O(\e^{\,|n|\ln^{-1}\!|n|})$ as $|n|\to\infty$.

Identificador

http://pure.qub.ac.uk/portal/en/publications/pointwise-universal-trigonometric-series(21ad3a28-64b8-4b44-b2ec-87c2431442b8).html

Idioma(s)

eng

Direitos

info:eu-repo/semantics/restrictedAccess

Fonte

Shkarin , S 2009 , ' Pointwise universal trigonometric series ' Journal of Mathematical Analysis and its Applications , vol 360 , no. 2 , pp. 754-758 .

Palavras-Chave #/dk/atira/pure/subjectarea/asjc/2600/2603 #Analysis #/dk/atira/pure/subjectarea/asjc/2600/2604 #Applied Mathematics
Tipo

article