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On approach regions for the conjugate Poisson integral and singular integrals

S. Ferrando, R. Jones, K. Reinhold (1996)

Studia Mathematica

Let ũ denote the conjugate Poisson integral of a function f L p ( ) . We give conditions on a region Ω so that l i m ( v , ε ) ( 0 , 0 ) ( v , ε ) Ω ũ ( x + v , ε ) = H f ( x ) , the Hilbert transform of f at x, for a.e. x. We also consider more general Calderón-Zygmund singular integrals and give conditions on a set Ω so that s u p ( v , r ) Ω | ʃ | t | > r k ( x + v - t ) f ( t ) d t | is a bounded operator on L p , 1 < p < ∞, and is weak (1,1).

On coincidence of p-module of a family of curves and p-capacity on the Carnot group.

Irina Markina (2003)

Revista Matemática Iberoamericana

The notion of the extremal length and the module of families of curves has been studied extensively and has given rise to a lot of applications to complex analysis and the potential theory. In particular, the coincidence of the p-module and the p-capacity plays an mportant role. We consider this problem on the Carnot group. The Carnot group G is a simply connected nilpotent Lie group equipped vith an appropriate family of dilations. Let omega be a bounded domain on G and Ko, K1 be disjoint non-empty...

On definitions of superharmonic functions

Seizô Itô (1975)

Annales de l'institut Fourier

Let A be an elliptic differential operator of second order with variable coefficients. In this paper it is proved that any A -superharmonic function in the Riesz-Brelot sense is locally summable and satisfies the A -superharmonicity in the sense of Schwartz distribution.

On essential norm of the Neumann operator

Dagmar Medková (1992)

Mathematica Bohemica

One of the classical methods of solving the Dirichlet problem and the Neumann problem in 𝐑 m is the method of integral equations. If we wish to use the Fredholm-Radon theory to solve the problem, it is useful to estimate the essential norm of the Neumann operator with respect to a norm on the space of continuous functions on the boundary of the domain investigated, where this norm is equivalent to the maximum norm. It is shown in the paper that under a deformation of the domain investigated by a diffeomorphism,...

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