Estimate of the approximation of periodic functions by negative Cesàro means

The problem of approximation of continuous functions by Cesàro (C,α)-means, −1 < α < 0, in terms of L _p and C-modulus of continuity is studied.     

Properties of Cesàro means of double Fourier series

The pointwise behavior of partial sums and Cesàro means of trigonometric series were studied in many papers. This paper deals with the behavior of rectangular Cesàro means at a point (x ₀, y ₀) for functions f(x, y) bounded in the square [?π; π]² and satisfying the condition |f(x ₀ + s, y ₀ + t) ? f(x ₀, y ₀)| ≤ ρ $ \left( {\sqrt {s^2 + t^2 } } \right) $ ^α , for some α ∈ (0, 1) and all s and t.     

Rate of pointwise approximation of functions by the Cesàro (C, β)-means of their Fourier series

e consider the interrelation between the smoothness of a function at a fixed point with the behavior at this point of the Cesàro (C, β)-means of the Fourier series of this function.     

On the Cesàro summability of the ultraspherical series

Summary The author has obtained theorems for Cesàro summability of the ultraspherical series which are analogous to those of Izumi and Sunouchi (2) in Fourier series.     

Negative order Cesàro means of double Fourier series and bounded generalized variation

Under study is the convergence of the negative order Cesàro means of the double trigonometric Fourier series of functions of bounded generalized Λ-variation.     

Cesàro summability of one- and two-dimensional Walsh-Fourier series

ВВОДьтсьp-кВАжИлОкАл ьНыЕ ОпЕРАтОРы И ОДНО МЕРНыЕ ДИАДИЧЕскИЕ МАРтИНг АльНыЕ пРОстРАНстВА хАРДИH _p . ДОкАжАНО, ЧтО ЕслИ сУБлИНЕИНыИ ОпЕРАтО РT p-кВАжИлОкАлЕН И ОгРА НИЧЕН ИжL _∞ ВL _∞, тО ОН ьВльЕтсь тАкжЕ ОгРАН ИЧЕННыМ ИжH _p ВL _p , (0<p<1). В кАЧЕстВЕ пРИ лОжЕНИь ДОкАжАНО, ЧтО МАксИМАльНыИ ОпЕРАт ОР ОДНОгО ЧЕжАРОВскОгО пАРАМЕтРА И МОДИФИцИ РОВАННых ЧЕжАРОВскИх сРЕДНИх МАРтИНгАлА ьВльЕтсь ОгРАНИЧЕННыМ ИжH _p ВL _p И ИМЕЕт слАБыИ тИп (L ₁,L ₁). Мы ВВОДИМ ДВУМЕРНыИ ДИА ДИЧЕскИИ гИБРИД пРОс тРАНстВ хАРДИH ₁ И пОкАжыВАЕМ, Ч тО МАксИМАльНыИ ОпЕРАт ОР сРЕДНИх ЧЕжАРО ДВУ МЕРНОИ ФУНкцИИ ИМЕЕт слАБыИ тИп (H ₁ ^# ,L ₁). тАк Мы пОлУЧАЕМ, Ч тО ДВУпАРАМЕтРИЧЕск ИЕ сРЕДНИЕ ЧЕжАРО ФУНкц ИИf ?H ₁ ^# ?L logL схОДьтсь пОЧтИ ВсУДУ к ИсхОДНОИ ФУНк цИИ.     

On the properties of the strong Cesàro summability and strong convergence of series

Говорят, что ряд \(\mathop \sum \limits_{k = 0}^\infty a_k \) сумм ируется к s в смысле (С, gа), gа >?1, если $$\sigma _n^{(k)} - s = o(1),n \to \infty ,$$ в смысле [C,α] _λ , α<0, λ>0, если $$\frac{1}{{n + 1}}\mathop \sum \limits_{k = 0}^n \left| {\sigma _k^{(\alpha - 1)} - s} \right|^\lambda = o(1),n \to \infty ,$$ и в смысле [C,0] _λ , λ>0, если $$\frac{1}{{n + 1}}\mathop \sum \limits_{k = 0}^n \left| {(k + 1)(s_k - 1) - k(s_{k - 1} - 1)} \right|^\lambda = o(1),n \to \infty ,$$ где σ _n ^(α) обозначаетn-ое ч езаровское среднее р яда. Суммируемость [C,α] _λ , α>?1, λ ≧1 о значает, что $$\mathop \sum \limits_{k = 0}^\infty k^{\lambda - 1} \left| {\sigma _k^{(\alpha )} - \sigma _{k - 1}^{(\alpha )} } \right|^\lambda< \infty .$$ В данной статье содер жится продолжение ис следований свойств [C,α] _λ -суммиру емо сти, которые начали Винн, Х ислоп, Флетт, Танович-М иллер и автор, в частности свя зей между указанными методами суммирования. Наконец, даны некотор ые простые приложени я к вопросам суммируемости ортог ональных рядов.     

Rate of Cesàro summability of double orthogonal series

Unimprovable estimates (in the class of double orthogonal series) are obtained on the rate of almost everywhere summability of orthogonal expansions of square-integrable functions by Cesàro methods of positive order. The conditions imposed on the coefficients are of classical type.     

Factorization of Cesàro and Hilbert matrices based on generalized Cesàro matrix

ABSTRACT

In this paper, we introduce factorizations for the Hilbert and Cesàro matrices based on generalized Cesàro matrix and as the application, we generalize the Hardy's inequality versus Hilbert's.     

Continuity in Λ-variation and summation of multiple Fourier series by Cesàro methods

We construct new examples of functions of bounded Λ-variation not continuous in Λ-variation. Using these examples, we show that, in the problem of the summability of multiple Fourier series by the Cesàro method of negative order, the condition of continuity in Λ-variation, is essential in contrast to the one-dimensional case.     

On weighted uniform Cesàro summability of Jacobi-Fourier series

The aim of this paper is to give weighted function spaces in which the sequence of Cesàro means of the Jacobi-Fourier series are uniformly convergent. Error estimate for the approximation will also be considered.     

A theorem on the absolute Cesàro summability of factored fourier series

Summary In this paper, the author proves a theorem on the absoluteCesàro summability of factoredFourier series. His theorem extends a theorem ofMatsumoto and generalizes a theorem ofPrasad andBhatt.     

On the summability by Cesàro methods of double series with respect to block-orthonormal systems

The extension of the coefficient test of Menshov and Kaczmarz ensuring the almost everywhere (C, 1, 1)-((C, 1, 0) or (C, 0, 1)) summability of double series with respect to block-orthonormal systems is studied.     

Lp convergence of Cesàro means on sphere

LetR ⁿ be n-dimensional Euclidean space with n>-3. Demote by Ω _n the unit sphere inR ⁿ. ForfɛL(Ω _n ) we denote by σ _N ^δ its Cesàro means of order σ for spherical harmonic expansions. The special value l = \tfracn - 22\lambda = \tfrac{{n - 2}}{2} of σ is known as the critical one. For 0<σ≤λ, we set p₀ = \tfrac2ld+ lp_0 = \tfrac{{2\lambda }}{{\delta + \lambda }} . This paper proves that

Tauberian Type Conditions Connecting Cesàro and Riesz Summability Methods of Different Orders

In the paper conditions are studied which ensure the equivalence of two given summability methods on the class of numerical series satisfying these conditions. One of these methods is the regular Cesàro method (C,w), which replaces the role of the convergence (C,0) the latter occurring in the classical Tauberian theorems. The other summability method considered is either the summability method (Rd,) by discrete Riesz means or the Cesàro method with (Rd,) with > w. New Tauberian type conditions are obtained under which the corresponding Tauberian theorems are proved.