Some quantities related to monotonicity and bounded variation of functions

The aim of this paper is to introduce and study some quantities connected with monotonicity and bounded variation of real functions. These quantities will also be considered for bounded subsets of spaces of bounded or continuous functions on a compact interval, equipped with the standard supremum norm. Several properties of such quantities are established, and possible applications are briefly sketched. Moreover, some relation with the theory of measures of noncompactness is discussed as well.     

On some measures of noncompactness in the Fréchet spaces of continuous functions

In this paper, the Fréchet spaces of continuous functions defined on a bounded or an unbounded interval, with values in the space of all real sequences, are considered. For those Fréchet spaces new regular measures of noncompactness are constructed and several properties of these measures are established. The results obtained are further applied to infinite systems of functional-integral equations.     

Solvability of a functional integral equation of fractional order in the class of functions having limits at infinity

A functional integral equation of fractional order is investigated in the space of real functions which are defined, continuous and bounded on the real half-axis. Using the technique of measures of noncompactness and the fixed point theorem of Darbo type we prove that the equation in question has solutions in the mentioned function space. Moreover, a suitable choice of a measure of noncompactness enables us to prove that those solutions tend to limits at infinity. An example illustrating our result is also given.     

Existence of mild solutions for semilinear differential equations with nonlocal and impulsive conditions

This paper is concerned with the existence of mild solutions for impulsive semilinear differential equations with nonlocal conditions. Using the technique of measures of noncompactness in Banach and Fréchet spaces of piecewise continuous functions, existence results are obtained both on bounded and unbounded intervals, when the impulsive functions and the nonlocal item are not compact in the space of piecewise continuous functions but they are continuous and Lipschitzian with respect to some measure of noncompactness, and the linear part generates only a strongly continuous evolution system.     

Global asymptotic stability of solutions of a functional integral equation

Using the technique of measures of noncompactness we prove a theorem on the existence and global asymptotic stability of solutions of a functional integral equation. The investigations are placed in the Banach space of real functions defined, continuous and bounded on an unbounded interval. A few realizations of the result obtained are indicated.     

Strongly Generated Banach Spaces and Measures of Noncompactness

To generalize the Hausdorff measure of noncompactness to other classes of bounded sets (like e. g. conditionally weakly compact or Asplund sets), we introduce Grothendieck classes. We deduce integral inequalities for quantities (called Grothendieck measures) related to these classes. As a by-product, we can answer a question concerning the measure of noncompactness for linear T : X → Y introduced in [14], and generalize a theorem about weak solutions of differential equations in Banach spaces.     

On existence of integrable solutions of a functional integral equation under Carathéodory conditions

We study the solvability of a functional integral equation in the space of Lebesgue integrable functions on an unbounded interval. Using the conjunction of the technique of measures of weak noncompactness with the classical Schauder fixed point principle we show that the equation in question is solvable in the mentioned function space. Our existence result is obtained under the assumption that functions involved in the investigated functional integral equation satisfy Carathéodory conditions. Moreover, that result generalizes several ones obtained earlier in many research papers and monographs.     

Measures of noncompactness and essential pseudospectra on Banach space

In this research article, we work with the notion of the measures of noncompactness in order to establish some results concerning the essential pseudospectra of closed, densely defined linear operators in the Banach space. We start by giving a refinement of the definition of the essential pseudospectra by means of the measure of noncompactness, and we give sufficient conditions on the perturbed operator to have its invariance. Copyright © 2013 John Wiley & Sons, Ltd.     

Inequivalent measures of noncompactness

Two homogeneous measures of noncompactness ?? and ?? on an infinite dimensional Banach space X are called ??equivalent?? if there exist positive constants b and c such that b ??(S)??? ??(S)??? c ??(S) for all bounded sets ${S\subset X}$ . If such constants do not exist, the measures of noncompactness are ??inequivalent.?? We ask a foundational question which apparently has not previously been considered: For what infinite dimensional Banach spaces do there exist inequivalent measures of noncompactness on X? We provide here the first examples of inequivalent measures of noncompactness. We prove that such inequivalent measures exist if X is a Hilbert space; or if (??, ??,???) is a general measure space, 1??? p??? ??, and X?=?L ^p (??, ??,???); or if K is a compact Hausdorff space and X?=?C(K); or if K is a compact metric space, 0?<??? ?? 1, and X?=?C ^0,??(K), the Banach space of H?lder continuous functions with H?lder exponent ??. We also prove the existence of such inequivalent measures of noncompactness if ?? is an open subset of ${\mathbb{R}^n}$ and X is the Sobolev space W ^m,p (??). Our motivation comes from questions about existence of eigenvectors of homogeneous, continuous, order-preserving cone maps f : C??C and from the closely related issue of giving the proper definition of the ??cone essential spectral radius?? of such maps. These questions are considered in the companion paper [28]; see, also, [27].     

A Family of Measures of Noncompactness in the Space {L^1_{\text{loc}}(\mathbb{R}_+)} and its Application to Some Nonlinear Volterra Integral Equation

The aim of this paper is to study a new family of measures of noncompactness in the space ${L^1_{\text{loc}}(\mathbb{R}_+)}$ consisting of all real functions locally integrable on ${\mathbb{R}_+}$ , equipped with a suitable topology. As an example of applications of the technique associated with that family of measures of noncompactness, we study the existence of solutions of a nonlinear Volterra integral equation in the space ${L^1_{\text{loc}}(\mathbb{R}_+)}$ . The obtained result generalizes several ones obtained earlier with help of other methods.     

Generalized measures of noncompactness of sets and operators in Banach spaces

New measures of noncompactness for bounded sets and linear operators, in the setting of abstract measures and generalized limits, are constructed. A quantitative version of a classical criterion for compactness of bounded sets in Banach spaces by R. S. Phillips is provided. Properties of those measures are established and it is shown that they are equivalent to the classical measures of noncompactness. Applications to summable families of Banach spaces, interpolations of operators and some consequences are also given.     

On quadratic integral equation of fractional orders

We present an existence theorem for a nonlinear quadratic integral equations of fractional orders, arising in the queuing theory and biology, in the Banach space of real functions defined and continuous on a bounded and closed interval. The concept of measure of noncompactness and a fixed point theorem due to Darbo are the main tool in carrying out our proof.     

几类非紧性测度之间的比较性质

首先列举了几类不同意义下的非紧性测度,并对这几种非紧性测度作了比较,得到了两个重要的比较性质.     

On Urysohn-Volterra fractional quadratic integral equations

In this paper the authors study a fractional quadratic integral equation of Urysohn-Volterra type. They show that the integral equation has at least one monotonic solution in the Banach space of all real functions defined and continuous on the interval $[0,1]$. The main tools in the proof are a fixed point theorem due to Darbo and a monotonicity measure of noncompactness.     

On graph measures in banach spaces and description of essential spectra of multidimensional transport equation

In this paper, we define new measures called respectively graph measure of noncompactness and graph measure of weak noncompactness. Moreover, we apply the obtained results to discuss the incidence of some perturbation results realized in [2] on the behavior of essential spectra of such closed densely defined linear operators on Banach spaces. These results are exploited to investigate the essential spectra of a multidimensional neutron transport operator on L₁ spaces.     

On characterization and properties of replete Wallman spaces

The subset of lattice regular zero-one valued measures on an algebra generated by a lattice (a Wallman-type space) which integrates all lattice continuous functions on an arbitrary setX is introduced and some properties of it are presented.Then repleteness of certain Wallman spaces is considered and used in finally establishing conditions whereby the space of lattice regular zero-one valued measures on the algebra generated by a lattice which are countably additive (a Wallman-type space) is realcompact.     

On existence and asymptotic behaviour of solutions of a functional integral equation

The paper contains a result on the existence and asymptotic behaviour of solutions of a functional integral equation. That result is proved under rather general hypotheses. The main tools used in our considerations are the concept of a measure of noncompactness and the classical Schauder fixed point principle. The investigations of the paper are placed in the space of continuous and tempered functions on the real half-line. We prove an existence result which generalizes several ones concerning functional integral equations and obtained earlier by other authors. The applicability of our result is illustrated by some examples.     

Geometrical coefficients and the structure of the fixed-point set of asymptotically regular mappings in Banach spaces

It is shown that if E is a separable and uniformly convex Banach space with Opial’s property and C is a nonempty bounded closed convex subset of E, then for some asymptotically regular self-mappings of C the set of fixed points is not only connected but even a retract of C. Our results qualitatively complement, in the case of a uniformly convex Banach space, a corresponding result presented in [T. Domínguez, M.A. Japón, G. López, Metric fixed point results concerning measures of noncompactness mappings, in: W.A. Kirk, B. Sims (Eds.), Handbook of Metric Fixed Point Theory, Kluwer Acad. Publishers, Dordrecht, 2001, pp. 239-268].     

半非紧测度与集值AM映象

本文以半非紧测度为工具研究一类非线性集值映象的性质，然后把所得结果用于证明微分包含的解的存在性     

Existence of mild solutions for the semilinear nonlocal problem in Banach spaces

In this paper we study the existence of mild solutions of the semilinear nonlocal initial value problem on a bounded and on an unbounded interval. In our considerations we apply a new calculation method based on the technique of modulus of continuity in conjunction with idea of the family of measures of noncompactness in Fréchet space. The results obtained in this paper generalize several ones obtained earlier by many authors.