On boundedness of weighted Hardy operator in and regularity condition.
On continuous composition operators
Let I ⊂ ℝ be an interval, Y be a normed linear space and Z be a Banach space. We investigate the Banach space Lip₂(I,Z) of all functions ψ: I → Z such that , where [r,s,t;ψ]:= ((s-r)ψ(t)+(t-s)ψ(r)-(t-r)ψ(s))/((t-r)(t-s)(s-r)). We show that ψ ∈ Lip₂(I,Z) if and only if ψ is differentiable and its derivative ψ’ is Lipschitzian. Suppose the composition operator N generated by h: I × Y → Z, (Nφ)(t):= h(t,φ(t)), maps the set (I,Y) of all affine functions φ: I → Y into Lip₂(I,Z). We prove that if N is...
On convergence of iterates of the Frobenius-Perron operator for expanding mappings
On dyadic spaces and almost Milyutin spaces
On Erb's uncertainty principle
We improve a result of Erb, concerning an uncertainty principle for orthogonal polynomials. The proof uses numerical range and a decomposition of some multiplication operators as a difference of orthogonal projections.
On essential norm of the Neumann operator
One of the classical methods of solving the Dirichlet problem and the Neumann problem in 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 extreme operators
On integral operators with operator-valued kernels.
On Integral Representations and a priori Lipschitz Estimates for the Canonical Solution of the ...-Equation.
On invariant functions and ergodic measures of Markov operators on C(X)
On isometric domains of positive operators on -spaces
On isometric domains of positive operators on orlicz spaces
On isomorphisms of some Köthe function F-spaces
We prove that if Köthe F-spaces X and Y on finite atomless measure spaces (ΩX; ΣX, µX) and (ΩY; ΣY; µY), respectively, with absolute continuous norms are isomorphic and have the property (for µ = µX and µ = µY, respectively) then the measure spaces (ΩX; ΣX; µX) and (ΩY; ΣY; µY) are isomorphic, up to some positive multiples. This theorem extends a result of A. Plichko and M. Popov concerning isomorphic classification of L p(µ)-spaces for 0 < p < 1. We also provide a new class of F-spaces...
On boundedness for convolutions with kernels having singularities on a sphere
For the convolution operators with symbols , 0 ≤ Re α < n, , we construct integral representations and give the exact description of the set of pairs (1/p,1/q) for which the operators are bounded from to .
On Lebesgue pseudonorms on
On Musielak-Orlicz spaces isometric to L2 or L∞.
It is proved that a Musielak-Orlicz space LΦ of real valued functions which is isometric to a Hilbert space coincides with L2 up to a weight, that is Φ(u,t) = c(t) u2. Moreover it is shown that any surjective isometry between LΦ and L∞ is a weighted composition operator and a criterion for LΦ to be isometric to L∞ is presented.
On nonintegrality of functions of some integral and partially integral operators.
On norm attaining operators acting from to C (S)
On Operators in Bochner Spaces
On operators on