Necessary and sufficient Tauberian conditions for the logarithmic summability of functions and sequences

Ferenc Móricz

Displaying similar documents to “Necessary and sufficient Tauberian conditions for the logarithmic summability of functions and sequences”

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It is proved that the multi-dimensional maximal Fejér operator defined in a cone is bounded from the amalgam Hardy space $W (h_{p}, ℓ_{\infty})$ to $W (L_{p}, ℓ_{\infty})$ . This implies the almost everywhere convergence of the Fejér means in a cone for all $f \in W (L ₁, ℓ_{\infty})$ , which is larger than $L ₁ (ℝ^{d})$ .

On the Nörlund means of Vilenkin-Fourier series

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We prove and discuss some new $(H_{p}, L_{p})$ -type inequalities of weighted maximal operators of Vilenkin-Nörlund means with non-increasing coefficients ${q_{k} : k \geq 0}$ . These results are the best possible in a special sense. As applications, some well-known as well as new results are pointed out in the theory of strong convergence of such Vilenkin-Nörlund means. To fulfil our main aims we also prove some new estimates of independent interest for the kernels of these summability results. In the special cases of...

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Ordinary convergence follows from statistical summability (C,1) in the case of slowly decreasing or oscillating sequences

Ferenc Móricz (2004)

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Schmidt’s Tauberian theorem says that if a sequence (xk) of real numbers is slowly decreasing and $l i m_{n \to \infty} (1 / n) \sum_{k = 1}^{n} x_{k} = L$ , then $l i m_{k \to \infty} x_{k} = L$ . The notion of slow decrease includes Hardy’s two-sided as well as Landau’s one-sided Tauberian conditions as special cases. We show that ordinary summability (C,1) can be replaced by the weaker assumption of statistical summability (C,1) in Schmidt’s theorem. Two recent theorems of Fridy and Khan are also corollaries of our Theorems 1 and 2. In the Appendix, we present a new proof...

Pointwise Fourier inversion of distributions on spheres

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Given a distribution $T$ on the sphere we define, in analogy to the work of Łojasiewicz, the value of $T$ at a point $ξ$ of the sphere and we show that if $T$ has the value $τ$ at $ξ$ , then the Fourier-Laplace series of $T$ at $ξ$ is Abel-summable to $τ$ .

A note on the $[τ, f (x)]$ means

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A note on a critical problem with natural growth in the gradient

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The paper analyzes the influence on the meaning of natural growth in the gradient of a perturbation by a Hardy potential in some elliptic equations. Indeed, in the case of the Laplacian the natural problem becomes $- Δ u - Λ_{N} \frac{u}{{| x |}^{2}} = {|\nabla u + \frac{N - 2}{2} \frac{u}{{| x |}^{2}} x|}^{2} {| x |}^{(N - 2) / 2} + λ f (x)$ in $Ω$ , $u = 0$ on $\partial Ω$ , $Λ_{N} = {((N - 2) / 2)}^{2}$ . This problem is a particular case of problem (2). Notice that $(N - 2) / 2$ is optimal as coefficient and exponent on the right hand side.

Complex series and connected sets

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CONTENTSPREFACE..........................................................................................................................................................................3INTRODUCTION............................................................................................................................................................. 41. Notation. 2. Subject of the paper.Chapter I. DECOMPOSITION OF Σ INTO $Σ_{1}$ , $Σ_{2}$ , $Σ_{3}$ , $Σ_{4}$ INESSENTIAL RESTRICTIONOF GENERALITY ...............................................................................................................................................................

A characterization of reflexive spaces of operators

Janko Bračič, Lina Oliveira (2018)

Czechoslovak Mathematical Journal

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We show that for a linear space of operators $ℳ \subseteq ℬ (ℋ_{1}, ℋ_{2})$ the following assertions are equivalent. (i) $ℳ$ is reflexive in the sense of Loginov-Shulman. (ii) There exists an order-preserving map $Ψ = (ψ_{1}, ψ_{2})$ on a bilattice $Bil (ℳ)$ of subspaces determined by $ℳ$ with $P \leq ψ_{1} (P, Q)$ and $Q \leq ψ_{2} (P, Q)$ for any pair $(P, Q) \in Bil (ℳ)$ , and such that an operator $T \in ℬ (ℋ_{1}, ℋ_{2})$ lies in $ℳ$ if and only if $ψ_{2} (P, Q) T ψ_{1} (P, Q) = 0$ for all $(P, Q) \in Bil (ℳ)$ . This extends the Erdos-Power type characterization of weakly closed bimodules over a nest algebra to reflexive spaces.

A Note on VLO Functions

Francesca Angrisani, Giacomo Ascione (2018)

Rendiconto dell’Accademia delle Scienze Fisiche e Matematiche

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Inspired by a result from Leibov, we ﬁnd that the supremum deﬁning the $B L O$ norm in $[0,1]$ is actually attained by a speciﬁc sub-interval of $[0,1]$ for $f\in VLO([0,1])$

The "Full Clarkson-Erdős-Schwartz Theorem" on the closure of non-dense Müntz spaces

Tamás Erdélyi (2003)

Studia Mathematica

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Denote by spanf₁,f₂,... the collection of all finite linear combinations of the functions f₁,f₂,... over ℝ. The principal result of the paper is the following. Theorem (Full Clarkson-Erdős-Schwartz Theorem). Suppose ${(λ_{j})}_{j = 1}^{\infty}$ is a sequence of distinct positive numbers. Then $s p a n 1, x^{λ ₁}, x^{λ ₂}, . . .$ is dense in C[0,1] if and only if $\sum_{j = 1}^{\infty} (λ_{j}) / (λ_{j} ² + 1) = \infty$ . Moreover, if $\sum_{j = 1}^{\infty} (λ_{j}) / (λ_{j} ² + 1) < \infty$ , then every function from the C[0,1] closure of $s p a n 1, x^{λ ₁}, x^{λ ₂}, . . .$ can be represented as an analytic function on z ∈ ℂ ∖ (-∞, 0]: |z| < 1 restricted to (0,1). This result improves an...

Structure of Cesàro function spaces: a survey

Sergey V. Astashkin, Lech Maligranda (2014)

Banach Center Publications

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Geometric structure of Cesàro function spaces $C e s_{p} (I)$ , where I = [0,1] and [0,∞), is investigated. Among other matters we present a description of their dual spaces, characterize the sets of all q ∈ [1,∞] such that $C e s_{p} [0, 1]$ contains isomorphic and complemented copies of $l_{q}$ -spaces, show that Cesàro function spaces fail the fixed point property, give a description of subspaces generated by Rademacher functions in spaces $C e s_{p} [0, 1]$ .

On linear preservers of two-sided gut-majorization on $𝐌_{n, m}$

Asma Ilkhanizadeh Manesh, Ahmad Mohammadhasani (2018)

Czechoslovak Mathematical Journal

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For $X, Y \in 𝐌_{n, m}$ it is said that $X$ is gut-majorized by $Y$ , and we write $X ≺_{gut} Y$ , if there exists an $n$ -by- $n$ upper triangular g-row stochastic matrix $R$ such that $X = R Y$ . Define the relation $\sim_{gut}$ as follows. $X \sim_{gut} Y$ if $X$ is gut-majorized by $Y$ and $Y$ is gut-majorized by $X$ . The (strong) linear preservers of $≺_{gut}$ on $ℝ^{n}$ and strong linear preservers of this relation on $𝐌_{n, m}$ have been characterized before. This paper characterizes all (strong) linear preservers and strong linear preservers of $\sim_{gut}$ on $ℝ^{n}$ and $𝐌_{n, m}$ .