The first general introduction to stability of ordinary and functional differential equations by means of fixed point techniques, this text is suitable for advanced undergraduates and graduate students. 2006 edition.

Dedicated to Heinz Unger on occasion of his 65. birthday

This book's discussion of a broad class of differential equations includes linear differential and integrodifferential equations, fixed-point theory, and the basic stability and periodicity theory for nonlinear ordinary and functional differential equations.

This handbook consists of seventeen chapters written by eminent scientists from the international mathematical community, who present important research works in the field of mathematical analysis and related subjects, particularly in the Ulam stability theory of functional equations. The book provides an insight into a large domain of research with emphasis to the discussion of several theories, methods and problems in approximation theory, analytic inequalities, functional analysis, computational algebra and applications. The notion of stability of functional equations has its origins with S. M. Ulam, who posed the fundamental problem for approximate homomorphisms in 1940 and with D. H. Hyers, Th. M. Rassias, who provided the first significant solutions for additive and linear mappings in 1941 and 1978, respectively. During the last decade the notion of stability of functional equations has evolved into a very active domain of mathematical research with several applications of interdisciplinary nature. The chapters of this handbook focus mainly on both old and recent developments on the equation of homomorphism for square symmetric groupoids, the linear and polynomial functional equations in a single variable, the Drygas functional equation on amenable semigroups, monomial functional equation, the Cauchy–Jensen type mappings, differential equations and differential operators, operational equations and inclusions, generalized module left higher derivations, selections of set-valued mappings, D’Alembert’s functional equation, characterizations of information measures, functional equations in restricted domains, as well as generalized functional stability and fixed point theory.

Since the publication of my lecture notes, Functional Differential Equations in the Applied Mathematical Sciences series, many new developments have occurred. As a consequence, it was decided not to make a few corrections and additions for a second edition of those notes, but to present a more compre hensive theory. The present work attempts to consolidate those elements of the theory which have stabilized and also to include recent directions of research. The following chapters were not discussed in my original notes. Chapter 1 is an elementary presentation of linear differential difference equations with constant coefficients of retarded and neutral type. Chapter 4 develops the recent theory of dissipative systems. Chapter 9 is a new chapter on perturbed systems. Chapter 11 is a new presentation incorporating recent results on the existence of periodic solutions of autonomous equations. Chapter 12 is devoted entirely to neutral equations. Chapter 13 gives an introduction to the global and generic theory. There is also an appendix on the location of the zeros of characteristic polynomials. The remainder of the material has been completely revised and updated with the most significant changes occurring in Chapter 3 on the properties of solutions, Chapter 5 on stability, and Chapter lOon behavior near a periodic orbit.

This book's coverage of differential equations begins with the structure of the solution space and the stability and periodic properties of linear ordinary and Volterra differential equations.&Discusses the fixed-point theorems of Banach, Brouwer, Browder, Horn, Schauder, and Tychonov and concludes with the basic stability and periodicity theory for nonlinear ordinary and functional differential equations. 1985 edition.

Fixed point theory has a long history of being used in nonlinear differential equations, in order to prove existence, uniqueness, or other qualitative properties of solutions. However, using the contraction mapping principle for stability and asymptotic stability of solutions is of more recent appearance. Lyapunov functional methods have dominated the determination of stability for general nonlinear systems without solving the systems themselves. In particular, as functional differential equations (FDEs) are more complicated than ODEs, obtaining methods to determine stability of equations that are difficult to handle takes precedence over analytical formulas. Applying Lyapunov techniques can be challenging, and the Banach fixed point method has been shown to yield less restrictive criteria for stability of delayed FDEs. We will study how to apply the contraction mapping principle to stability under different conditions to the ones considered by previous authors. We will first extend a contraction mapping stability result that gives asymptotic stability of a nonlinear time-delayed scalar FDE which is linearly dominated by the last state of the system, in order to obtain uniform stability plus asymptotic stability. We will also generalize to the vector case. Afterwards we do further extension by considering an impulsively perturbed version of the previous result, and subsequently we shall use impulses to stabilize an unstable system, under a contraction method paradigm. At the end we also extend the method to a time dependent switched system, where difficulties that do not arise in non-switched systems show up, namely a dwell-time condition, which has already been studied by previous authors using Lyapunov methods. In this study, we will also deepen understanding of this method, as well as point out some other difficulties about using this technique, even for non-switched systems. The purpose is to prompt further investigations into this method, since sometimes one must consider more than one aspect other than stability, and having more than one stability criterion might yield benefits to the modeler.