Displaying similar documents to “BMO and commutators of martingale transforms”

Pointwise multipliers on weighted BMO spaces

Eiichi Nakai (1997)

Studia Mathematica

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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...

A theorem on weak type estimates for Riesz transforms and martingale transforms

Nicolas Th. Varopoulos (1981)

Annales de l'institut Fourier

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The Riesz transforms of a positive singular measure ν M ( R n ) satisfy the weak type inequality m j = 1 n | R j ν | &gt; λ C ν λ , λ &gt; 0 where m denotes Lebesgue measure and C is a positive constant only depending on m .