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On the pointwise strong approximation by (C,1)(E,1) means

Włodzimierz Łenski, Bogdan Roszak (2008)

Banach Center Publications

We present an estimate of the (C,1)(E,1)-strong means with mixed powers of the Fourier series of a function f L 2 π as a generalization of the result obtained by M. Yildrim and F. Karakus. Some corollaries on the norm approximation are also given.

On the Product of Functions in BMO and H 1

Aline Bonami, Tadeusz Iwaniec, Peter Jones, Michel Zinsmeister (2007)

Annales de l’institut Fourier

The point-wise product of a function of bounded mean oscillation with a function of the Hardy space H 1 is not locally integrable in general. However, in view of the duality between H 1 and B M O , we are able to give a meaning to the product as a Schwartz distribution. Moreover, this distribution can be written as the sum of an integrable function and a distribution in some adapted Hardy-Orlicz space. When dealing with holomorphic functions in the unit disc, the converse is also valid: every holomorphic...

On the product theory of singular integrals.

Alexander Nagel, Elias M. Stein (2004)

Revista Matemática Iberoamericana

We establish Lp-boundedness for a class of product singular integral operators on spaces M = M1 x M2 x . . . x Mn. Each factor space Mi is a smooth manifold on which the basic geometry is given by a control, or Carnot-Carathéodory, metric induced by a collection of vector fields of finite type. The standard singular integrals on Mi are non-isotropic smoothing operators of order zero. The boundedness of the product operators is then a consequence of a natural Littlewood- Paley theory on M. This in...

On the proof of Erdős' inequality

Lai-Yi Zhu, Da-Peng Zhou (2017)

Czechoslovak Mathematical Journal

Using undergraduate calculus, we give a direct elementary proof of a sharp Markov-type inequality p ' [ - 1 , 1 ] 1 2 p [ - 1 , 1 ] for a constrained polynomial p of degree at most n , initially claimed by P. Erdős, which is different from the one in the paper of T. Erdélyi (2015). Whereafter, we give the situations on which the equality holds. On the basis of this inequality, we study the monotone polynomial which has only real zeros all but one outside of the interval ( - 1 , 1 ) and establish a new asymptotically sharp inequality.

On the quantitative Fatou property

A. Kamaly, A. M. Stokolos (2002)

Colloquium Mathematicae

The result of this article together with [1] and [4] gives a full quantitative description of a Fatou type property for functions from Hardy classes in the upper half plane.

On the Quotient Function Employed in the Blind Source Separation Problem

Fujita, K. (2010)

Fractional Calculus and Applied Analysis

MSC 2010: 42C40, 94A12On the blind source separation problem, there is a method to use the quotient function of complex valued time-frequency informations of two ob-served signals. By studying the quotient function, we can estimate the number of sources under some assumptions. In our previous papers, we gave a mathematical formulation which is available for the sources with-out time delay. However, in general, we can not ignore the time delay. In this paper, we will reformulate our basic theorems...

On the Rademacher maximal function

Mikko Kemppainen (2011)

Studia Mathematica

This paper studies a new maximal operator introduced by Hytönen, McIntosh and Portal in 2008 for functions taking values in a Banach space. The L p -boundedness of this operator depends on the range space; certain requirements on type and cotype are present for instance. The original Euclidean definition of the maximal function is generalized to σ-finite measure spaces with filtrations and the L p -boundedness is shown not to depend on the underlying measure space or the filtration. Martingale techniques...

On the range of the Fourier transform connected with Riemann-Liouville operator

Lakhdar Tannech Rachdi, Ahlem Rouz (2009)

Annales mathématiques Blaise Pascal

We characterize the range of some spaces of functions by the Fourier transform associated with the Riemann-Liouville operator α , α 0 and we give a new description of the Schwartz spaces. Next, we prove a Paley-Wiener and a Paley-Wiener-Schwartz theorems.

On the rate of strong summability of double Fourier series

Włodzimierz Łenski, Maria Topolewska (1998)

Mathematica Bohemica

Estimates of the strong means of Marcinkiewicz type with the Cesaro means of negative order in one of the variables instead of square partial sums are obtained by characteristics constructed on the basis of moduli of continuity.

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