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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,...

On limits of L p -norms of an integral operator

Pavel Stavinoha (1994)

Applications of Mathematics

A recurrence relation for the computation of the L p -norms of an Hermitian Fredholm integral operator is derived and an expression giving approximately the number of eigenvalues which in absolute value are equal to the spectral radius is determined. Using the L p -norms for the approximation of the spectral radius of this operator an a priori and an a posteriori bound for the error are obtained. Some properties of the a posteriori bound are discussed.

On singular integrals of Calderón-type in Rn and BMO.

Steve Hofmann (1994)

Revista Matemática Iberoamericana

We prove Lp (and weighted Lp) bounds for singular integrals of the formp.v.  ∫Rn E (A(x) - A(y) / |x - y|) (Ω(x - y) / |x - y|n) f(y) dy,where E(t) = cos t if Ω is odd, and E(t) = sin t if Ω is even, and where ∇ A ∈ BMO. Even in the case that Ω is smooth, the theory of singular integrals with rough kernels plays a key role in the proof. By standard techniques, the trigonometric function E can then be replaced by a large class of smooth functions F. Some related operators are also considered. As...

On solutions of integral equations with analytic kernels and rotations

Nguyen Van Mau, Nguyen Minh Tuan (1996)

Annales Polonici Mathematici

We deal with a class of integral equations on the unit circle in the complex plane with a regular part and with rotations of the form (*)     x(t) + a(t)(Tx)(t) = b(t), where T = M n , k . . . M n m , k m and M n j , k j are of the form (3) below. We prove that under some assumptions on analytic continuation of the given functions, (*) is a singular integral equation for m odd and is a Fredholm equation for m even. Further, we prove that T is an algebraic operator with characteristic polynomial P T ( t ) = t ³ - t . By means of the Riemann boundary value...

On some structural properties of Banach function spaces and boundedness of certain integral operators

T. S. Kopaliani (2004)

Czechoslovak Mathematical Journal

In this paper the notions of uniformly upper and uniformly lower -estimates for Banach function spaces are introduced. Further, the pair ( X , Y ) of Banach function spaces is characterized, where X and Y satisfy uniformly a lower -estimate and uniformly an upper -estimate, respectively. The integral operator from X into Y of the form K f ( x ) = ϕ ( x ) 0 x k ( x , y ) f ( y ) ψ ( y ) d y is studied, where k , ϕ , ψ are prescribed functions under some local integrability conditions, the kernel k is non-negative and is assumed to satisfy certain additional...

On the Hardy-type integral operators in Banach function spaces.

Elena Lomakina, Vladimir Stepanov (1998)

Publicacions Matemàtiques

Characterization of the mapping properties such as boundedness, compactness, measure of non-compactness and estimates of the approximation numbers of Hardy-type integral operators in Banach function spaces are given.

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