Bøger af Jurgen Appell

The aim of this monograph is to give a thorough and self-contained account of functions of (generalized) bounded variation, the methods connected with their study, their relations to other important function classes, and their applications to various problems arising in Fourier analysis and nonlinear analysis. In the first part the basic facts about spaces of functions of bounded variation and related spaces are collected, the main ideas which are useful in studying their properties are presented, and a comparison of their importance and suitability for applications is provided, with a particular emphasis on illustrative examples and counterexamples. The second part is concerned with (sometimes quite surprising) properties of nonlinear composition and superposition operators in such spaces. Moreover, relations with Riemann-Stieltjes integrals, convergence tests for Fourier series, and applications to nonlinear integral equations are discussed. The only prerequisite for understanding this book is a modest background in real analysis, functional analysis, and operator theory. It is addressed to non-specialists who want to get an idea of the development of the theory and its applications in the last decades, as well as a glimpse of the diversity of the directions in which current research is moving. Since the authors try to take into account recent results and state several open problems, this book might also be a fruitful source of inspiration for further research.

Alfonso Vignoli - the Researcher, Teacher, and Friend.- How to Make Use of the Solution Set to Solve Boundary Value Problems.- On the Unique Solvability of Hammerstein Integral Equations with Non-Symmetric Kernels.- The Invariance of Domain for C1Fredholm Maps of Index Zero.- Positive Eigenfunctions for Some Unbounded Differential Operators.- Some Geometrical Properties of Rearrangement Invariant Spaces.- Strong Surjections and Nearness.- On the Vanishing Viscosity Approximation of a Time Dependent Hamilton-Jacobi Equation.- Some Remarks on a Nonlinear Model of Competitive Equilibrium.- Almost Discrete Convergence.- Nonlinear Stability of Eigenvalues of Compact Self-Adjoint Operators.- A Bifurcation Theorem for Lagrangian Intersections.- La valutazione di opzioni implicite nei mutui bancari.- Continuity of Near-Duality Maps and Characterizations of Ideal Spaces of Measurable Functions.- A Spectral Theory for Semilinear Operators and its Applications.- Feedback Stability of Closed Sets for Nonlinear Control Systems.- Two Mechanical Systems and Equivariant Degree.- On the Semilinear Dirichlet Problem for a Class of Nonlocal Operators Generating Dirichlet Forms.- Bifurcation for One-Parameter Families of Scalar Maps: A Geometric Viewpoint.- Mountain Pass and Linking Type Solutions for Semilinear Dirichlet Forms.- Self-Similar Measures in Quasi-Metric Spaces.- C1-Fredholm Maps and Bifurcation for Quasilinear Elliptic Equations on$${\mathbb{R}^n} $$.

Dieses Buch wendet sich an Studierende des Fachs Mathematik im ersten Semester und enthält das Basiswissen, welches in den Anfängervorlesungen behandelt und im Laufe des Studiums immer wieder gebraucht wird.Hauptsächlicher Gegenstand dieses Buches sind Mengen von Zahlen. Einerseits kennen wir Zahlen aus naiver Erfahrung und gehen täglich damit um. Andererseits haben diese Zahlen interessante Eigenschaften, deren Verständnis Kenntnisse über mathematische Grundstrukturen voraussetzen. Die Vermittlung dieser Kenntnisse ist ein wichtiges Ziel dieses Buches.Das Buch dient allerdings nicht nur der Einführung der wichtigsten Zahlbereiche von den natürlichen bis zu den komplexen Zahlen und darüber hinaus, sondern behandelt auch ausführlich den in der Mathematik fundamentalen Mengen- und Funktionsbegriff. Zudem können Sie sich schon an Begriffe und Techniken gewöhnen, die in den beiden mathematischen Grundvorlesungen Analysis und Lineare Algebra zentral sind.Ein besonderes Merkmal dieses Buches ist die Vielzahl der Beispiele und Gegenbeispiele. Einen neuen mathematischen Begriff kann man erfahrungsgemäß oft besser verstehen, wenn er zunächst anhand einfacher Beispiele und Gegenbeispiele erklärt wird, statt gleich in voller Allgemeinheit eingeführt zu werden. Ähnliches gilt für Übungsaufgaben: Neue Begriffe, Methoden und Ergebnisse lernt man nicht durch Lesen oder Zuhören, sondern nur durch den Umgang damit. Daher enthält das Buch ein Kapitel mit etwa 300 Übungsaufgaben. Zu einigen der etwas anspruchsvolleren Aufgaben finden Sie am Schluss des Buches Lösungshinweise.

The authors present a completely new and highly application-oriented field of nonlinear analysis. The work covers the theory of non-smooth input-output systems and presents various methods to non-standard applications in mathematics and physics. A particular focus lies on hysteresis and relay phenomena, electric circuits with diode nonlinearities, and biological systems with constraints.

This book is a self-contained account of knowledge of the theory of nonlinear superposition operators: a generalization of the notion of functions. The theory developed here is applicable to operators in a wide variety of function spaces, and it is here that the modern theory diverges from classical nonlinear analysis.

In view of the eminent importance of spectral theory of linear operators in many fields of mathematics and physics, it is not surprising that various attempts have been made to define and study spectra also for nonlinear operators. This book provides a comprehensive and self-contained treatment of the theory, methods, and applications of nonlinear spectral theory. The first chapter briefly recalls the definition and properties of the spectrum and several subspectra for bounded linear operators. Then some numerical characteristics for nonlinear operators are introduced which are useful for describing those classes of operators for which there exists a spectral theory. Since spectral values are closely related to solvability results for operator equations, various conditions for the local or global invertibility of a nonlinear operator are collected in the third chapter. The following two chapters are concerned with spectra for certain classes of continuous, Lipschitz continuous, or differentiable operators. These spectra, however, simply adapt the corresponding definitions from the linear theory which somehow restricts their applicability. Other spectra which are defined in a completely different way, but seem to have useful applications, are defined and studied in the following four chapters. The remaining three chapters are more application-oriented and deal with nonlinear eigenvalue problems, numerical ranges, and selected applications to nonlinear problems. The only prerequisite for understanding this book is a modest background in functional analysis and operator theory. It is addressed to non-specialists who want to get an idea of the development of spectral theory for nonlinear operators in the last 30 years, as well as a glimpse of the diversity of the directions in which current research is moving.