A companion of Ostrowski's inequality for mappings whose first derivatives are bounded and applications in numerical integration
A note on a general difference-functional equation.
A note on Hölder's inequality
A Note on Lipschitz Classes.
An elementary proof of the Harnack inequality for non-negative infinity-superharmonic functions.
An elementary proof of the preservation of Lipschitz constants by the Meyer-König and Zeller operators.
Approximate and Peano derivatives of nonintegral order
Let n be a nonnegative integer and let u ∈ (n,n+1]. We say that f is u-times Peano bounded in the approximate (resp. , 1 ≤ p ≤ ∞) sense at if there are numbers , |α| ≤ n, such that is in the approximate (resp. ) sense as h → 0. Suppose f is u-times Peano bounded in either the approximate or sense at each point of a bounded measurable set E. Then for every ε > 0 there is a perfect set Π ⊂ E and a smooth function g such that the Lebesgue measure of E∖Π is less than ε and f = g on Π....
Best possible sufficient conditions for the Fourier transform to satisfy the Lipschitz or Zygmund condition
We consider complex-valued functions f ∈ L¹(ℝ), and prove sufficient conditions in terms of f to ensure that the Fourier transform f̂ belongs to one of the Lipschitz classes Lip(α) and lip(α) for some 0 < α ≤ 1, or to one of the Zygmund classes zyg(α) and zyg(α) for some 0 < α ≤ 2. These sufficient conditions are best possible in the sense that they are also necessary in the case of real-valued functions f for which either xf(x) ≥ 0 or f(x) ≥ 0 almost everywhere.
Bi-Lipschitz Bijections of Z
It is shown that every bi-Lipschitz bijection from Z to itself is at a bounded L1 distance from either the identity or the reflection.We then comment on the group-theoretic properties of the action of bi-Lipschitz bijections.
Bi-Lipschitz embeddings of hyperspaces of compact sets
We study the bi-Lipschitz embedding problem for metric compacta hyperspaces. We observe that the compacta hyperspace K(X) of any separable, uniformly disconnected metric space X admits a bi-Lipschitz embedding in ℓ². If X is a countable compact metric space containing at most n nonisolated points, there is a Lipschitz embedding of K(X) in ; in the presence of an additional convergence condition, this embedding may be chosen to be bi-Lipschitz. By way of contrast, the hyperspace K([0,1]) of the...
Bi-Lipschitz mappings and quasinearly subharmonic functions.
Canonical Banach function spaces generated by Urysohn universal spaces. Measures as Lipschitz maps
It is proved (independently of the result of Holmes [Fund. Math. 140 (1992)]) that the dual space of the uniform closure of the linear span of the maps x ↦ d(x,a) - d(x,b), where d is the metric of the Urysohn space of diameter r, is (isometrically if r = +∞) isomorphic to the space of equivalence classes of all real-valued Lipschitz maps on . The space of all signed (real-valued) Borel measures on is isometrically embedded in the dual space of and it is shown that the image of the embedding...
Characterization of globally Lipschitzian composition operators in the Banach space
We give a characterization of the globally Lipschitzian composition operators acting in the space
Construction of functions with prescribed Hölder and chirp exponents.
We show that the Hölder exponent and the chirp exponent of a function can be prescribed simultaneously on a set of full measure, if they are both lower limits of continuous functions. We also show that this result is optimal: In general, Hölder and chirp exponents cannot be prescribed outside a set of Hausdorff dimension less than one. The direct part of the proof consists in an explicit construction of a function determined by its orthonormal wavelet coefficients; the optimality is the direct consequence...
Constructive function theory and spline systems
Continuity of Nemyckij's operator in Hölder spaces
Differentiability points of a distance function
Distortion function and quasisymmetric mappings
We study the relationship between the distortion function and normalized quasisymmetric mappings. This is part of a new method for solving the boundary values problem for an arbitrary K-quasiconformal automorphism of a generalized disc on the extended complex plane.
Formules sommatoires et systèmes de numération liés aux substitutions
Functions satisfying an integral Lipschitz condition