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On weighted inequalities for operators of potential type

Shiying Zhao (1996)

Colloquium Mathematicae

In this paper, we discuss a class of weighted inequalities for operators of potential type on homogeneous spaces. We give sufficient conditions for the weak and strong type weighted inequalities sup_{λ>0} λ|{x ∈ X : |T(fdσ)(x)|>λ }|_{ω}^{1/q} ≤ C (∫_{X} |f|^{p}dσ)^{1/p} and (∫_{X} |T(fdσ)|^{q}dω )^{1/q} ≤ C (∫_X |f|^{p}dσ )^{1/p} in the cases of 0 < q < p ≤ ∞ and 1 ≤ q < p < ∞, respectively, where T is an operator of potential type, and ω and σ are Borel measures on the homogeneous...

Pluriharmonic functions on symmetric tube domains with BMO boundary values

Ewa Damek, Jacek Dziubański, Andrzej Hulanicki, Jose L. Torrea (2002)

Colloquium Mathematicae

Let 𝓓 be a symmetric Siegel domain of tube type and S be a solvable Lie group acting simply transitively on 𝓓. Assume that L is a real S-invariant second order operator that satisfies Hörmander's condition and annihilates holomorphic functions. Let H be the Laplace-Beltrami operator for the product of upper half planes imbedded in 𝓓. We prove that if F is an L-Poisson integral of a BMO function and HF = 0 then F is pluriharmonic. Some other related results are also considered.

Pointwise estimates for densities of stable semigroups of measures

Paweł Głowacki, Waldemar Hebisch (1993)

Studia Mathematica

Let μ t be a symmetric α-stable semigroup of probability measures on a homogeneous group N, where 0 < α < 2. Assume that μ t are absolutely continuous with respect to Haar measure and denote by h t the corresponding densities. We show that the estimate h t ( x ) t Ω ( x / | x | ) | x | - n - α , x≠0, holds true with some integrable function Ω on the unit sphere Σ if and only if the density of the Lévy measure of the semigroup belongs locally to the Zygmund class LlogL(N╲e). The problem turns out to be related to the properties of the maximal...

Pointwise multipliers on weighted BMO spaces

Eiichi Nakai (1997)

Studia Mathematica

Let E and F be spaces of real- or complex-valued functions defined on a set X. A real- or complex-valued function g defined on X is called a pointwise multiplier from E to F if the pointwise product fg belongs to F for each f ∈ E. We denote by PWM(E,F) the set of all pointwise multipliers from E to F. Let X be a space of homogeneous type in the sense of Coifman-Weiss. For 1 ≤ p < ∞ and for ϕ : X × + + , we denote by b m o ϕ , p ( X ) the set of all functions f L l o c p ( X ) such that s u p a X , r > 0 1 / ϕ ( a , r ) ( 1 / μ ( B ( a , r ) ) ʃ B ( a , r ) | f ( x ) - f B ( a , r ) | p d μ ) 1 / p < , where B(a,r) is the ball centered at a and of...

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