Displaying similar documents to “The work of José Luis Rubio de Francia (II).”

Vector-valued inequalities with weights.

Luz M. Fernández-Cabrera, José L. Torrea (1993)

Publicacions Matemàtiques

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This paper deals with the following problem: Let T be a given operator. Find conditions on v(x) (resp. u(x)) such that ∫ |Tf(x)|pu(x) dx ≤ C ∫ |f(x)|pv(x) dx is satisfied for some u(x) (resp. v(x)). Using vector-valued inequalities the problem is solved for: Carleson's maximal operator of Fourier partial sums, Littlewood-Paley square functions, Hilbert transform of functions...

The converse of the Hölder inequality and its generalizations

Janusz Matkowski (1994)

Studia Mathematica

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Let (Ω,Σ,μ) be a measure space with two sets A,B ∈ Σ such that 0 < μ (A) < 1 < μ (B) < ∞ and suppose that ϕ and ψ are arbitrary bijections of [0,∞) such that ϕ(0) = ψ(0) = 0. The main result says that if ʃ Ω x y d μ ≤ ϕ - 1 ( ʃ Ω ϕ ∘ x d μ ) ψ - 1 ( ʃ Ω ψ ∘ x d μ ) for all μ-integrable nonnegative step functions x,y then ϕ and ψ must be conjugate power functions. If the measure space (Ω,Σ,μ) has one of the following properties: (a) μ (A) ≤ 1 for every A ∈ Σ of finite measure; (b) μ (A) ≥ 1 for every A ∈ Σ of positive measure, then...