منابع مشابه
Universal series by trigonometric system in weighted Lμ1 spaces
is said to be universal in X with respect to rearrangements, if for any f ∈ X the members of (1.1) can be rearranged so that the obtained series ∑∞ k=1 fσ(k) converges to f by norm of X . Definition 1.2. The series (1.1) is said to be universal (in X) in the usual sense, if for any f ∈ X there exists a growing sequence of natural numbers nk such that the sequence of partial sums with numbers nk...
متن کاملRearrangements of Trigonometric Series and Trigonometric Polynomials
Abstract. The paper is related to the following question of P. L. Ul’yanov: is it true that for any 2π-periodic continuous function f there is a uniformly convergent rearrangement of its trigonometric Fourier series? In particular, we give an affirmative answer if the absolute values of Fourier coefficients of f decrease. Also, we study a problem how to choose m terms of a trigonometric polynom...
متن کاملLacunary Trigonometric Series. Ii
where E c [0, 1] is any given set o f positive measure and {ak} any given sequence of real numbers. This theorem was first proved by R. Salem and A. Zygmund in case of a -0, where {flk} satisfies the so-called Hadamard's gap condition (cf. [4], (5.5), pp. 264-268). In that case they also remarked that under the hypothesis (1.2) the condition (1.3) is necessary for the validity of (1.5) (cf. [4]...
متن کاملOn Lacunary Trigonometric Series.
1. Fundamental theorem. In a recent paper f I have proved the theorem that if a lacunary trigonometric series CO (1) X(a* cos nk6 + bk sin nk9) (nk+x/nk > q > 1, 0 ^ 0 ^ 2ir) 4-1 has its partial sums uniformly bounded on a set of 0 of positive measure, then the series (2) ¿(a*2 + bk2) k-l converges. The proof was based on the following lemma (which was not stated explicitly but is contained in ...
متن کاملTrigonometric Series via Laplace Transforms
Costas J. Efthimiou Department of Physics University of Central Florida Orlando, FL 32816 USA Introduction In another NOTE in this MAGAZINE, the author presented a method [2] that uses the Laplace transform and allows one to find exact values for a large class of convergent series of rational terms. Recently, in this MAGAZINE too, Lesko and Smith [3] revisited the method and demonstrated an ext...
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ژورنال
عنوان ژورنال: Journal of Mathematical Analysis and Applications
سال: 1970
ISSN: 0022-247X
DOI: 10.1016/0022-247x(70)90064-8