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On convergence for the square root of the Poisson kernel in symmetric spaces of rank 1

Jan-Olav Rönning (1997)

Studia Mathematica

Let P(z,β) be the Poisson kernel in the unit disk , and let P λ f ( z ) = ʃ P ( z , φ ) 1 / 2 + λ f ( φ ) d φ be the λ -Poisson integral of f, where f L p ( ) . We let P λ f be the normalization P λ f / P λ 1 . If λ >0, we know that the best (regular) regions where P λ f converges to f for a.a. points on ∂ are of nontangential type. If λ =0 the situation is different. In a previous paper, we proved a result concerning the convergence of P 0 f toward f in an L p weakly tangential region, if f L p ( ) and p > 1. In the present paper we will extend the result to symmetric spaces X of...

On fractional differentiation and integration on spaces of homogeneous type.

A. Eduardo Gatto, Carlos Segovia, Stephen Vági (1996)

Revista Matemática Iberoamericana

In this paper we define derivatives of fractional order on spaces of homogeneous type by generalizing a classical formula for the fractional powers of the Laplacean [S1], [S2], [SZ] and introducing suitable quasidistances related to an approximation of the identity. We define integration of fractional order as in [GV] but using quasidistances related to the approximation of the identity mentioned before.We show that these operators act on Lipschitz spaces as in the classical cases. We prove that...

On maximal functions over circular sectors with rotation invariant measures

Hugo A. Aimar, Liliana Forzani, Virginia Naibo (2001)

Commentationes Mathematicae Universitatis Carolinae

Given a rotation invariant measure in n , we define the maximal operator over circular sectors. We prove that it is of strong type ( p , p ) for p > 1 and we give necessary and sufficient conditions on the measure for the weak type ( 1 , 1 ) inequality. Actually we work in a more general setting containing the above and other situations.

On positive Rockland operators

Pascal Auscher, A. ter Elst, Derek Robinson (1994)

Colloquium Mathematicae

Let G be a homogeneous Lie group with a left Haar measure dg and L the action of G as left translations on L p ( G ; d g ) . Further, let H = dL(C) denote a homogeneous operator associated with L. If H is positive and hypoelliptic on L 2 we prove that it is closed on each of the L p -spaces, p ∈ 〈 1,∞〉, and that it generates a semigroup S with a smooth kernel K which, with its derivatives, satisfies Gaussian bounds. The semigroup is holomorphic in the open right half-plane on all the L p -spaces, p ∈ [1,∞]. Further extensions...

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