Meir-Keeler condensing operators and applications

Motivated by the open question posed by H. K. XU in [39] (Question 2:8), Belhadj, Ben Amar and Boumaiza introduced in [5] the concept of Meir-Keeler condensing operator for self-mappings in a Banach space via an arbitrary measure of weak noncompactness. In this paper, we introduce the concept of Meir- Keeler condensing operator for nonself-mappings in a Banach space via a measure of weak noncompactness and we establish fixed point results under the condition of Leray-Schauder type. Some basic hybrid fixed point theorems involving the sum as well as the product of two operators are also presented. These results generalize the results on the lines of Krasnoselskii and Dhage. An application is given to nonlinear hybrid linearly perturbed integral equations and an example is also presented.

Solvability of functional-integral equations (fractional order) using measure of noncompactness

We investigate the solutions of functional-integral equation of fractional order in the setting of a measure of noncompactness on real-valued bounded and continuous Banach space. We introduce a new μ-set contraction operator and derive generalized Darbo fixed point results using an arbitrary measure of noncompactness in Banach spaces. An illustration is given in support of the solution of a functional-integral equation of fractional order.

Two-layer modal logics: from fuzzy logics to a general framework

The idea of two-layer modal logics is inspired by the treatment of probability inside mathematical fuzzy logic, pioneered by Hajek and recentlystudied by numerous authors in numerous papers. Such logics are used in order to deal with a certain property of formulas of the base logic using a suitable `upper' logic (the seminal example being the probability of classical events formalized inside Lukasiewicz logic). The primary aim of this paper is to provide a new general framework for two-layer modal logics that encompasses the current state of the art and paves the way for future development. Diverting for the area of mathematical fuzzy logic, we show how one can construct such modal logic over an arbitrary non-classical logic (under certain technical requirements) with a modality interpreted by an arbitrary measure. We equip the resulting logics with a semantics of measured Kripke frames and prove corresponding completeness theorems. As an illustration of our results, we reprove Hajek's completeness result for Fuzzy Probability logic over Lukasiewicz logic.

THE CRAMÉR–WOLD THEOREM ON QUADRATIC SURFACES AND HEISENBERG UNIQUENESS PAIRS

Two measurable sets $S,\unicode[STIX]{x1D6EC}\subseteq \mathbb{R}^{d}$ form a Heisenberg uniqueness pair, if every bounded measure $\unicode[STIX]{x1D707}$ with support in $S$ whose Fourier transform vanishes on $\unicode[STIX]{x1D6EC}$ must be zero. We show that a quadratic hypersurface and the union of two hyperplanes in general position form a Heisenberg uniqueness pair in $\mathbb{R}^{d}$. As a corollary we obtain a new, surprising version of the classical Cramér–Wold theorem: a bounded measure supported on a quadratic hypersurface is uniquely determined by its projections onto two generic hyperplanes (whereas an arbitrary measure requires the knowledge of a dense set of projections). We also give an application to the unique continuation of eigenfunctions of second-order PDEs with constant coefficients.

Approximation of capacities with additive measures

For a space of non-additive regular measures on a metric compactum with the Prokhorov-style metric, it is shown that the problem of approximation of arbitrary measure with an additive measure on a fixed finite subspace reduces to linear optimization problem with parameters dependent on the values of the measure on a finite number of sets. An algorithm for such an approximation, which is more efficient than the straighforward usage of simplex method, is presented.

On lp-convergence of Bernstein-Durrmeyer operators with respect to arbitrary measure

We consider Bernstein-Durrmeyer operators with respect to arbitrary measure on the simplex in the space Rd. We obtain estimates for rate of convergence in the corresponding weighted Lp-spaces, 1 ? p < ?.