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Absolute continuity for elliptic-caloric measures

Caroline Sweezy (1996)

Studia Mathematica

A Carleson condition on the difference function for the coefficients of two elliptic-caloric operators is shown to give absolute continuity of one measure with respect to the other on the lateral boundary. The elliptic operators can have time dependent coefficients and only one of them is assumed to have a measure which is doubling. This theorem is an extension of a result of B. Dahlberg [4] on absolute continuity for elliptic measures to the case of the heat equation. The method of proof is an...

Absolute convergence of multiple Fourier integrals

Yurii Kolomoitsev, Elijah Liflyand (2013)

Studia Mathematica

Various new sufficient conditions for representation of a function of several variables as an absolutely convergent Fourier integral are obtained. The results are given in terms of L p integrability of the function and its partial derivatives, each with a different p. These p are subject to certain relations known earlier only for some particular cases. Sharpness and applications of the results obtained are also discussed.

Adaptive Deterministic Dyadic Grids on Spaces of Homogeneous Type

Richard Lechner, Markus Passenbrunner (2014)

Bulletin of the Polish Academy of Sciences. Mathematics

In the context of spaces of homogeneous type, we develop a method to deterministically construct dyadic grids, specifically adapted to a given combinatorial situation. This method is used to estimate vector-valued operators rearranging martingale difference sequences such as the Haar system.

Almost Everywhere Convergence Of Convolution Powers Without Finite Second Moment

Christopher M. Wedrychowicz (2011)

Annales de l’institut Fourier

Bellow and Calderón proved that the sequence of convolution powers μ n f ( x ) = k μ n ( k ) f ( T k x ) converges a.e, when μ is a strictly aperiodic probability measure on such that the expectation is zero, E ( μ ) = 0 , and the second moment is finite, m 2 ( μ ) < . In this paper we extend this result to cases where m 2 ( μ ) = .

Alternative characterisations of Lorentz-Karamata spaces

David Eric Edmunds, Bohumír Opic (2008)

Czechoslovak Mathematical Journal

We present new formulae providing equivalent quasi-norms on Lorentz-Karamata spaces. Our results are based on properties of certain averaging operators on the cone of non-negative and non-increasing functions in convenient weighted Lebesgue spaces. We also illustrate connections between our results and mapping properties of such classical operators as the fractional maximal operator and the Riesz potential (and their variants) on the Lorentz-Karamata spaces.

An application of the Fourier transform to optimization of continuous 2-D systems

Vitali Dymkou, Michael Dymkov (2003)

International Journal of Applied Mathematics and Computer Science

This paper uses the theory of entire functions to study the linear quadratic optimization problem for a class of continuous 2D systems. We show that in some cases optimal control can be given by an analytical formula. A simple method is also proposed to find an approximate solution with preassigned accuracy. Some application to the 1D optimization problem is presented, too. The obtained results form a theoretical background for the design problem of optimal controllers for relevant processes.

An embedding relation for bounded mean oscillation on rectangles

Benoît F. Sehba (2014)

Annales Polonici Mathematici

In the two-parameter setting, we say a function belongs to the mean little BMO if its mean over any interval and with respect to any of the two variables has uniformly bounded mean oscillation. This space has been recently introduced by S. Pott and the present author in relation to the multiplier algebra of the product BMO of Chang-Fefferman. We prove that the Cotlar-Sadosky space b m o ( N ) of functions of bounded mean oscillation is a strict subspace of the mean little BMO.

An estimation for a family of oscillatory integrals

Magali Folch-Gabayet, James Wright (2003)

Studia Mathematica

Let K be a Calderón-Zygmund kernel and P a real polynomial defined on ℝⁿ with P(0) = 0. We prove that convolution with Kexp(i/P) is continuous on L²(ℝⁿ) with bounds depending only on K, n and the degree of P, but not on the coefficients of P.

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